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Abstract:

A toner including a core particle and projections at a surface of the
core particle is provided. The core particle includes a binder resin and
a colorant. The binder resin includes a crystalline resin as a major
component. Each of the projections consists of a fine resin particle. An
average length of long sides of the projections is not less than 0.15
μm and less than 0.5 μm. A standard deviation of lengths of the
long sides of the projections is 0.2 or less. A surface coverage of the
toner with the projections is within a range of 30 to 90%.

Claims:

1. A toner, comprising: a core particle, the core particle including a
binder resin and a colorant, the binder resin including a crystalline
resin as a major component; and projections at a surface of the core
particle, each of the projections consisting of a fine resin particle,
wherein an average length of long sides of the projections is not less
than 0.15 μm and less than 0.5 μm, wherein a standard deviation of
lengths of the long sides of the projections is 0.2 or less, and wherein
a surface coverage of the toner with the projections is within a range of
30 to 90%.

2. The toner according to claim 1, wherein the toner satisfies the
following formula 50.ltoreq.Tm1.ltoreq.70 (1) wherein Tm1 (° C.)
represents a melting point of the crystalline resin.

3. The toner according to claim 1, wherein the toner satisfies the
following formula (2): 10,000.ltoreq.Mw≦40,000 (2) wherein Mw
represents a weight average molecular weight of the crystalline resin.

4. The toner according to claim 1, wherein the crystalline resin includes
a first crystalline resin and a second crystalline resin, wherein a
weight average molecular weight of the second crystalline resin is
greater than that of the first crystalline resin, and wherein the first
crystalline resin includes a crystalline polyester.

5. The toner according to claim 4, wherein the second crystalline resin
includes a crystalline resin having urethane and/or urea bond in its
backbone.

6. The toner according to claim 4, wherein the second crystalline resin
is obtained by elongating a modified crystalline resin having an
isocyanate group on its terminal.

7. The toner according to claim 1, wherein the crystalline resin includes
a first crystalline resin and a second crystalline resin, wherein a
weight average molecular weight of the second crystalline resin is
greater than that of the first crystalline resin, and wherein the first
crystalline resin includes a crystalline resin having urethane and/or
urea bond in its backbone.

8. The toner according to claim 1, wherein, when the toner is subjected
to first and second heating processes by a differential scanning
calorimeter, a ratio (Tsh2nd/Tsh1st) of a second shoulder temperature
(Tsh2nd) of a second peak of melting heat observed in the second heating
process to a first shoulder temperature (Tsh1st) of a first peak of
melting heat observed in the first heating process is within a range of
0.90 to 1.10.

9. The toner according to claim 1, wherein the toner satisfies the
following formulae: 5.0.times.10.sup.4<G'(70)<5.0.times.10.sup.5
1.0.times.10.sup.3<G'(160)<1.0.times.10.sup.4 wherein G'(70) and
G'(160) represent a storage elastic modulus (Pa) of the toner at
70.degree. C. and 160.degree. C., respectively.

11. The toner according to claim 1, wherein the toner satisfies the
following formula (4): Tm2<Tg (4) wherein Tm2 (° C.)
represents a melting point of the toner and Tg (° C.) represents a
glass transition temperature of the fine resin particle.

12. The toner according to claim 1, wherein the fine resin particle
includes a resin obtained by polymerizing a mixture of monomers including
styrene monomer in an amount 70% by weight or more.

13. The toner according to claim 1, wherein the fine resin particle
accounts for 1 to 20% by weight of the toner.

14. An image forming apparatus, comprising: a latent image bearing member
adapted to bear a latent image; a charger adapted to uniformly charge a
surface of the latent image bearing member; an irradiator adapted to
irradiate the charged surface of the latent image bearing member with
light based on image data to write an electrostatic latent image thereon;
a developing device containing the toner according to claim 1, the
developing device being adapted to develop the electrostatic latent image
with the toner to form a toner image; a transfer device adapted to
transfer the toner image from the latent image bearing member onto a
transfer medium; and a fixing device adapted to fix the toner image on
the transfer medium.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application is based on and claims priority pursuant to
35 U.S.C. §119 to Japanese Patent Application No. 2011-245712, filed
on Nov. 9, 2011, in the Japan Patent Office, the entire disclosure of
which is hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

[0002] 1. Technical Field

[0003] The present disclosure relates to a toner for developing
electrostatic latent images in the field of electrophotography,
electrostatic recording, and electrostatic printing. The present
disclosure also related to an image forming apparatus containing the
toner.

[0006] Recently, such full-color image forming apparatuses are widely used
and required to produce images having much higher definition. To meet the
requirement for higher-definition images, toner has been developed to be
much more spherical and smaller. Thus, polymerization processes, which
are generally capable of producing spherical and small toner, such as
suspension polymerization, emulsion polymerization, and dispersion
polymerization processes, are widely employed as toner production process
recently in place of pulverization processes.

[0007] However, toner produced by a polymerization process
("polymerization toner") has some drawbacks. One drawback is poor
transfer efficiency due to its small size and large adhesive force.
Another drawback is poor cleanability (i.e., removability from a
photoreceptor) due to its spherical shape. Another drawback is that
polymerization toner particles are likely to cause background fouling in
resulting images because their surfaces are undesirably low in electric
resistivity.

[0008] Electrophotographic developing processes are of two types:
one-component developing process and two-component developing process.
One-component developing process can be reliably performed with a simple
and compact apparatus because a process of mixing toner and carrier
particles is not needed, which meets a potential requirement for
energy-saving and cost reduction. Thus, toner adaptable for one-component
developing process is being developed recently.

[0009] In one-component developing process, toner particles get through a
pressurized gap formed between a developing sleeve and a regulation blade
so that the toner particles are charged. At the same time, however, the
toner particles are undesirably stressed and degraded.

[0010] Moreover, the toner particles may undesirably adhere to the
regulation blade or fuse on the developing sleeve without forming a
desirable thin layer thereon.

[0011] On the other hand, for the purpose of saving energy, toner is
required to be fixable at temperatures as low as possible. To meet this
requirement, there has been an attempt to include a
low-melting-temperature binder resin in toner. As usable
low-melting-temperature binder resins, crystalline resins have been
proposed that can rapidly melt upon application of heat. There has been
another attempt to include a crystalline resin as a primary binder resin
in toner.

[0012] Such toner having low-temperature fixability is also required to
have heat-resistant storage stability. Heat-resistant storage stability
may be improved by reforming toner surface by increasing the glass
transition temperature thereof. However, merely increasing the glass
transition temperature of toner surface would not prevent deformation of
toner especially in a high-temperature and high-humidity condition, such
as a case in which toner or toner cartridge is in transportation during
which toner is generally exposed to a certain pressure. There have been
attempts to increase the glass transition temperature and melting
temperature of toner in whole.

[0014] JP-2011-123483-A describes a toner having projections at surface of
the toner. Each of the projections is formed of fine vinyl resin
particles.

[0015] JP-2005-215298-A describes a toner having a core including a
crystalline polyester and a shell layer including an amorphous polymer.

SUMMARY OF THE INVENTION

[0016] In accordance with some embodiments, a toner including a core
particle and projections at a surface of the core particle is provided.
The core particle includes a binder resin and a colorant. The binder
resin includes a crystalline resin as a major component. Each of the
projections consists of a fine resin particle. An average length of long
sides of the projections is not less than 0.15 μm and less than 0.5
μm. A standard deviation of lengths of the long sides of the
projections is 0.2 or less. A surface coverage of the toner with the
projections is within a range of 30 to 90%.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0017] A more complete appreciation of the disclosure and many of the
attendant advantages thereof will be readily obtained as the same becomes
better understood by reference to the following detailed description when
considered in connection with the accompanying drawings, wherein:

[0018]FIG. 1 is a cross-sectional schematic view of a toner according to
an embodiment;

[0019]FIG. 2 is a schematic view of a process cartridge according to an
embodiment;

[0020]FIG. 3 is a schematic view of an image forming apparatus according
to an embodiment;

[0021]FIG. 4 is a schematic view of an image forming part included in the
image forming apparatus illustrated in FIG. 3;

[0022]FIG. 5 is a schematic view of a developing device included in the
image forming part illustrated in FIG. 4;

[0023]FIG. 6 is a schematic view of a process cartridge according to an
embodiment; and

[0024]FIG. 7 is a schematic view of a SEM image of a toner particle
according to an embodiment.

DETAILED DESCRIPTION

[0025] Embodiments of the present invention are described in detail below
with reference to accompanying drawings. In describing embodiments
illustrated in the drawings, specific terminology is employed for the
sake of clarity. However, the disclosure of this patent specification is
not intended to be limited to the specific terminology so selected, and
it is to be understood that each specific element includes all technical
equivalents that operate in a similar manner and achieve a similar
result.

[0026] For the sake of simplicity, the same reference number will be given
to identical constituent elements such as parts and materials having the
same functions and redundant descriptions thereof omitted unless
otherwise stated.

[0027] According to an embodiment, a toner including a core particle and
projections at a surface of the core particle is provided. The core
particle includes a binder resin and a colorant. The binder resin
includes a crystalline resin as a major component. Each of the
projections consists of a fine resin particle. An average length of long
sides of the projections is not less than 0.15 μm and less than 0.5
μm. A standard deviation of the lengths of the long sides of the
projections is 0.2 or less. A surface coverage of the toner with the
projections is within a range of 30 to 90%.

[0028] The toner provides a good combination of fixability and heat
resistance. The toner also provides uniform chargeability and
environmental stability.

[0029] With such a configuration in which fine resin particles are forming
projections at the surface of a core particle including a crystalline
resin as a major component, the toner provides low-temperature
fixability, chargeability, filming resistance, cleanability,
heat-resistant storage stability, and high-quality image at the same
time.

[0030] In some cases, a crystalline polyester resin formed from aliphatic
monomers rather than aromatic monomers are employed as the crystalline
resin for the purpose of improving low-temperature fixability of the
toner. Such a crystalline polyester resin formed from aliphatic monomers
is generally poor at chargeability. However, even in this case, the toner
can provide excellent chargeability by forming the fine resin particles
from styrene monomer that have good chargeability. The wide surface area
of the toner owing to the presence of the projections also contributes to
improvement of chargeability of the toner.

[0031] When the surface coverage of the toner with the projections is
within a range of 30 to 90%, the fine resin particles cover the surface
of the toner while forming spaces between each other and prevent
constituents of the core particle (e.g., a release agent) from exuding
from the toner. Due to the presence of the projections, the core particle
is rarely exposed to frictional forces under normal conditions and
therefore the release agents as well as the crystalline resin are
prevented from contaminating other members. The release agent exudes from
the toner only when the toner is exposed to heat and pressure to be fixed
on a recording medium. Because the fine resin particles do not completely
cover the core particle and form spaces between each other, the fine
resin particles do not prevent the release agent from exuding from the
toner.

[0032] As described above, the toner includes a core particle and
projections at a surface of the core particle. Each of the projections
consists of a fine resin particle.

[0033]FIG. 1 is a cross-sectional schematic view of the toner according
to an embodiment.

[0034] The core particle includes a binder resin. The binder resin
includes a crystalline resin as a major component. Each of the
projections consists of a fine resin particle. According to an
embodiment, the fine resin particle includes an amorphous resin.

[0035] In this specification, when the binder resin includes a crystalline
resin as a major component, it means that the crystalline resin accounts
for 50% by weight or more of the toner. When the crystalline resin
accounts for 50% by weight or more of the toner, the toner provides a
good combination of heat-resistant storage stability and low-temperature
fixability. Also, colored resin particles composing the toner have high
homogeneity. By contrast, when the crystalline resin accounts for less
than 50% by weight of the toner, it may be difficult for the toner to
provide both heat-resistant storage stability and low-temperature
fixability at the same time.

[0036] The average length of long sides of the projections is not less
than 0.15 μm and less than 0.5 μm, or 0.3 μm or less. When the
average length is 0.5 μm or more, the projections are distributed over
the core particle too sparsely. Such a toner is not resistant to stress
from a toner regulating blade and likely to fracture. The projections do
not satisfactorily reform the surface of the toner.

[0037] The standard deviation of the lengths of the long sides of the
projections is 0.2 or less, or 0.1 or less. When the standard deviation
exceeds 0.2, the surface of the toner is non-uniform. Such a toner being
melted on a recording medium is likely to peel off due to the
non-uniformity.

[0038] The surface coverage of the toner with the projections is within a
range of 30 to 90%, 40 to 80%, or 50 to 70%. When the surface coverage
falls below 30%, the toner cannot be charged sufficiently and background
fouling occurs in resulting image. Also, the toner cannot be prevented
from sticking to a toner regulating blade and cannot keep good qualities
under pressure or heat. When the surface coverage exceeds 90%, the
crystalline resin in the core particle is prevented from being fixed on a
recording medium at lower temperatures.

[0040] A crystalline polyester resin can be obtained by a polycondensation
of a polyol with a polycarboxylic acid. Usable polyols include, but are
not limited to, aliphatic diols such as ethylene glycol, 1,2-propylene
glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, neopentyl glycol,
1,4-butenediol, 1,10-decanediol, and 1,9-nonanediol. In some embodiments,
1,4-butanediol, 1,6-hexanediol, or 1,8-octanediol is preferably used. In
some embodiments, 1,6-hexanediol, ethylene glycol, 1,10-decanediol, or
1,9-nonanediol is more preferably used. Usable polycarboxylic acids
include, but are not limited to, aromatic dicarboxylic acids such as
phthalic acid, isophthalic acid, and terephthalic acid; and C2-C12
aliphatic carboxylic acids such as adipic acid and 1,10-dodecanedioic
acid. Aliphatic carboxylic acids are more advantageous in increasing
crystallinity.

[0041] A crystalline polyurea resin can be obtained from a reaction among
a diamine, a diisocyanate, and optional trivalent or more valent amine
and isocyanate.

[0042] Usable amines include, but are not limited to, aliphatic amines
such as C2-C18 aliphatic diamines and aromatic amines such as C6-C20
aromatic diamines. Trivalent or more valent amines are also usable.

[0045] Usable trivalent or more valent amines include, but are not limited
to, polyamide polyamines, such as a low-molecular-weight polyamide
polyamine obtained from a condensation of a dicarboxylic acid (e.g.,
dimer acid) with an excessive amount of (i.e., 2 mol or more per 1 mol of
the acid) a polyamine (e.g., an alkylenediamine, a polyalkylene
polyamide); and polyether polyamines, such as a cyanoethylated or
hydrogenated polyether polyol (e.g., polyalkylene glycol).

[0046] In this specification, the crystalline resin is defined as a resin
having a local maximum peak in its endothermic curve obtained by
differential scanning calorimetry (DSC), which indicates that the resin
has a melting point. As to an amorphous resin, by contrast, its
endothermic curve is gradual and does not have local maximum peak, which
indicates that the resin has a glass transition point rather than a
melting point.

[0047] According to some embodiments, the crystalline resin has a melting
point (Tm1) within a range of 50 to 70° C., or 55 to 65° C.
When the melting point is 50° C. or more, the toner particles
neither deform nor stick together even in a high-temperature condition
such as in summer. When the melting point is 70° C. or less, the
toner is well fixable on recording media.

[0048] According to some embodiments, the crystalline resin has a weight
average molecular weight within a range of 10,000 to 40,000. When the
weight average molecular weight is 10,000 or more, heat-resistant storage
stability of the toner is good. When the weight average molecular weight
is 40,000 or less, low-temperature fixability of the toner is good.

[0049] According to some embodiments, the crystalline resin accounts for
50% by weight or more, 60% by weight or more, or 65% by weight or more,
of the toner. When the crystalline resin accounts for 50% by weight or
more of the toner, the toner provides both low-temperature fixability and
heat-resistant storage stability.

[0050] The core particle may further include a resin other than the
crystalline resin. Usable resins include amorphous polyester resins, for
example.

[0051] Usable amorphous polyester resins include either homopolymers of
amorphous polyester units or block copolymers of amorphous polyester
units with other units. Homopolymers of amorphous polyester units are
more advantageous in terms of homogeneity of resulting toner particles.
Usable amorphous polyester resins are not limited in molecular structure
so long as crystallinity is expressed.

[0052] An amorphous polyester resin can be obtained from a reaction
between a polyol and a polycarboxylic acid.

[0054] In accordance with some embodiments, the toner is prepared by the
steps of: dissolving or dispersing constituents of the core particle,
such as a binder resin, a colorant, a release agent, etc., in an organic
solvent to prepare an oil phase; dispersing the oil phase in an aqueous
medium to prepare a dispersion liquid containing droplets of the oil
phase (hereinafter "core droplets" for the sake of simplicity); mixing
the dispersion liquid containing core droplets with another dispersion
liquid containing fine resin particles so that the fine resin particles
are adhered to the surfaces of the core droplets; and removing the
organic solvent from the core droplets to obtain core particles having
the projections at their surfaces.

[0055] The projections are effectively formed as the fine resin particles
are swelled or dissolved by the organic solvent. The resulting toner
particles are uniformly chargeable and well fixable on recording media
while keeping heat resistance.

[0056] According to another embodiment, the toner is prepared by forming
core particles by a dissolution suspension process and mixing the core
particles with a dispersion liquid containing fine resin particles in the
presence of an organic solvent to form projections. The fine resin
particles may include a relatively large amount of styrene units so as to
be poorly compatible with the core particles.

[0057] The projections may be formed of fine particles of a vinyl polymer
having a relatively high hardness. In this case, the toner is prevented
from sticking to a regulating blade or a developing sleeve.

[0058] In accordance with some embodiments, the crystalline resin includes
a first crystalline resin and a second crystalline resin, the weight
average molecular weight (Mw) of which is greater than that of the first
crystalline resin. The first crystalline resin improves low-temperature
fixability and the second crystalline resin improves hot offset
resistance.

[0059] According to an embodiment, the first crystalline resin is a
crystalline polyester and the second crystalline resin is a crystalline
resin having urethane and/or urea bond in its backbone. The crystalline
resin having urethane and/or urea bond in its backbone may be obtained by
elongating a modified crystalline resin having an isocyanate group on its
terminal.

[0060] The first crystalline resin may also be a crystalline resin having
urethane and/or urea bond in its backbone.

[0061] In some embodiments, the first crystalline resin has a weight
average molecular weight (Mw) within a range of 10,000 to 40,000, 15,000
to 35,000, or 20,000 to 30,000, in view of low-temperature fixability and
heat-resistant storage stability of the toner. When Mw falls below
10,000, heat-resistant storage stability of the toner may deteriorate.
When Mw exceeds 40,000, low-temperature fixability of the toner may
deteriorate.

[0062] In some embodiments, the second crystalline resin has a weight
average molecular weight (Mw) within a range of 40,000 to 300,000, or
50,000 to 150,000, in view of low-temperature fixability and
heat-resistant storage stability of the toner. When Mw falls below
40,000, hot offset resistance of the toner may deteriorate. When Mw
exceeds 300,000, the toner may not sufficiently melt at low temperatures
and may be fixed on a recording medium with a weak force, causing peeling
of the toner image.

[0063] In some embodiments, the difference in Mw between the first and
second crystalline resins is 5,000 or more, or 10,000 or more. When the
difference is less than 5,000, it is likely that a temperature range
within which the toner is fixable is narrowed.

[0064] In some embodiments, the mixing ratio of the first crystalline
resin to the second crystalline resins is 95/5 to 70/30. When the mixing
ratio of the first crystalline resin is too large, hot offset resistance
of the toner may deteriorate. When the ratio of the first crystalline
resin is too small, low-temperature fixability of the toner may
deteriorate.

[0065] The binder resin may further include a modified crystalline resin
having urethane and/or urea group, for adjusting viscoelasticity of the
toner. A modified crystalline resin having urethane and/or urea group may
be directly included in the binder resin. Alternatively, a relatively
low-molecular-weight modified crystalline resin having an isocyanate
group on its terminal (hereinafter "prepolymer (A)") along with an amine
(B) may be mixed in the binder resin and then subjected to elongating
and/or cross-linking reactions to become a modified crystalline resin
having urethane and/or urea group during or after the process of forming
toner particles. In the latter case, the resulting modified crystalline
resin has a relatively high molecular weight and it can be easily
included in the toner.

[0066] The prepolymer (A) having an isocyanate group may be a reaction
product of a polyester having an active hydrogen group, which is a
polycondensation product of a polyol (1) with a polycarboxylic acid (2),
with a polyisocyanate (3). The active hydrogen group may be, for example,
a hydroxyl group (e.g., an alcoholic hydroxyl group, a phenolic hydroxyl
group), an amino group, a carboxyl group, or a mercapto group. In some
embodiments, an alcoholic hydroxyl group is employed.

[0068] In some embodiments, the equivalent ratio [NCO]/[OH] of isocyanate
groups [NCO] from the polyisocyanate (3) to hydroxyl groups [OH] from the
polyester is 5/1 to 1/1, 4/1 to 1.2/1, or 2.5/1 to 1.5/1. When [NCO]/[OH]
exceeds 5, low-temperature fixability of the toner may deteriorate. When
[NCO]/[OH] falls below 1, hot offset resistance of the toner may
deteriorate because urea content in the modified polyester is too low. In
some embodiments, the content of units from the polyisocyanate (3) in the
prepolymer is 0.5 to 40% by weight, 1 to 30% by weight, or 2 to 20% by
weight. When the content falls below 0.5% by weight, hot offset
resistance of the toner may deteriorate. When the content exceeds 40% by
weight, low-temperature fixability of the toner may deteriorate.

[0069] In some embodiments, the average number of isocyanate groups
included in one molecule of the prepolymer (A) is 1 or more, 1.5 to 3, or
1.8 to 2.5. When the average number of isocyanate groups falls below 1,
hot offset resistance of the toner may deteriorate because molecular
weight of the elongated and/or cross-linked modified polyester is too
low.

[0070] The amine (B) serves as an elongating and/or cross-linking agent.
The amine may be, for example, a diamine (B1), a polyamine (B2) having 3
or more valences, an amino alcohol (B3), an amino mercaptan (B4), an
amino acid (B5), or a blocked amine (B6) in which the amino group in any
of the amines (B1) to (B5) is blocked.

[0078] In some embodiments, the equivalent ratio [NCO]/[NHx] of isocyanate
groups [NCO] from the prepolymer (A) to amino groups [NHx] from the amine
(B) is 1/2 to 2/1, 1.5/1 to 1/1.5, or 1.2/1 to 1/1.2. When [NCO]/[NHx]
exceeds 2 or falls below 1/2, hot offset resistance of the toner may
deteriorate because the molecular weight of the urea-modified polyester
is too low.

[0079] According to some embodiments, the projections are formed of fine
particles of a vinyl resin. Fine particles of a vinyl resin can be
obtained by polymerizing a mixture of monomers primarily including
aromatic compounds having a vinyl-polymerizable functional group.

[0080] In some embodiments, the aromatic compounds having a
vinyl-polymerizable functional group accounts for 70 to 100% by weight,
90 to 100% by weight, or 95 to 100% by weight, of the mixture. When the
content of the aromatic compounds having a vinyl-polymerizable functional
group is less than 70% by weight of the mixture, chargeability of the
toner may be poor.

[0083] Among these compounds, styrene is easily available and highly
reactive.

[0084] The mixture of monomers may further include compounds having both a
vinyl-polymerizable functional group and an acid group (hereinafter "acid
monomers") in an amount of 0 to 7% by weight. In some embodiments, the
content of the acid monomers is 0 to 4% by weight of the mixture. In some
embodiments, no acid monomer is included in the mixture. When the content
of the acid monomers exceeds 7% by weight of the mixture, the resulting
fine vinyl resin particles have high dispersion stability and are not
likely to adhere to oil droplets in an aqueous phase at normal
temperature. Even in a case in which such fine vinyl resin particles are
adhered to oil droplets, the fine vinyl resin particles may easily
release therefrom through the succeeding processes of solvent removal,
washing, drying, and external treatment. When the content of the acid
monomers is 4% by weight or less of the mixture, the resulting fine vinyl
resin particles are environmentally stable in terms of chargeability.

[0085] The acid group in the acid monomer may be, for example, carboxyl
group, sulfonic group, or phosphoric group.

[0088] Two or more of these compounds can be used in combination. Among
these compounds, methoxypolyethylene glycol methacrylate, divinylbenzene,
methyl methacrylate, and butyl acrylate are highly reactive and easily
available.

[0089] Monomers having an ethylene oxide ("EO") chain, such as
phenoxyalkylene glycol acrylate, phenoxyalkylene glycol methacrylate,
phenoxypolyalkylene glycol acrylate, and phenoxypolyalkylene glycol
methacrylate, may also be used for controlling compatibility of the
resulting fine vinyl resin particles with the core particles. The content
of such monomers may be 10% by weight or less, 5% by weight or less, or
2% by weight or less, of the mixture of monomers. When the content of
such monomers exceeds 10% by weight of the mixture, polar groups may be
too rich at the surface of the toner, which results in deterioration of
environmental stability of the toner. Moreover, the fine vinyl resin
particles are too highly compatible with the core particles to be
prevented from being embedded therein. Monomers having an ester bond,
such as 2-acroyloxyethyl succinate and 2-methacryloyloxyethyl phthalate,
are also usable for controlling compatibility of the resulting fine vinyl
resin particles with the core particles. The content of such monomers may
be 10% by weight or less, 5% by weight or less, or 2% by weight or less,
of the mixture of monomers. When the content of such monomers exceeds 10%
by weight of the mixture, polar groups may be too rich at the surface of
the toner, which results in deterioration of environmental stability of
the toner. Moreover, the fine vinyl resin particles are too highly
compatible with the core particles to be prevented from being embedded
therein.

[0090] A dispersion liquid of fine vinyl resin particles may be properly
diluted or condensed before being mixed with a dispersion liquid of core
particles. In some embodiments, the concentration of fine vinyl resin
particles in the dispersion liquid thereof is 5 to 30% by weight, or 8 to
20% by weight. When the concentration of fine vinyl resin particles falls
below 5% by weight, the concentration of organic solvent changes
significantly at mixing the two dispersion liquids and the fine vinyl
resin particles are prevented from adhering to the core particles. When
the concentration of fine vinyl resin particles exceeds 30% by weight,
the fine vinyl resin particles are likely not to be uniformly dispersed
in the dispersion liquid of core particles and are prevented from
adhering to the core particles.

[0091] The amount of surfactant for preparing the core droplets may be 7%
by weight or less, 6% by weight or less, or 5% by weight or less, of the
aqueous medium. When the amount of surfactant is too large, the lengths
of the long sides of the projections are significantly varied.

[0092] When the fine resin particles have high compatibility with the core
particles, there is a possibility that projections with a desired shape
cannot be formed. The composition of the monomer mixture and/or the
polarity and molecular structure of binder resin are properly controlled
so as to reduce compatibility between the fine resin particles and the
core particles.

[0093] Additionally, the fine resin particles are designed so as not to be
excessively dissolved in organic solvents. If the fine resin particles
are well soluble in organic solvents, projections with a desired shape
cannot be formed.

[0094] Fine vinyl resin particles can be prepared by the following
processes (a) to (f).

[0095] (a) Directly subject a mixture of monomers to a polymerization,
such as a suspension polymerization, an emulsion polymerization, a seed
polymerization, or a dispersion polymerization, to obtain a dispersion
liquid of fine vinyl resin particles.

[0096] (b) Previously subject a mixture of monomers to a polymerization to
prepare a vinyl resin, pulverize the resin into particles by a mechanical
rotary pulverizer or a jet pulverizer, and classify the particles by
size.

[0097] (c) Previously subject a mixture of monomers to a polymerization to
prepare a vinyl resin, dissolve the resin in a solvent to prepare a resin
solution, and atomize the resin solution.

[0098] (d) Previously subject a mixture of monomers to a polymerization to
prepare a vinyl resin, dissolve the resin in a solvent to prepare a resin
solution and further add the solvent to the resin solution, or dissolve
the resin in a solvent by application of heat to prepare a resin solution
and cool the resin solution, to precipitate fine particles of the resin,
and remove the solvent.

[0099] (e) Previously subject a mixture of monomers to a polymerization to
prepare a vinyl resin, dissolve the resin in a solvent to prepare a resin
solution, disperse the resin solution in an aqueous medium in the
presence of a dispersant, and remove the solvent by application of heat
and/or reduction of pressure.

[0100] (f) Previously subject a mixture of monomers to a polymerization to
prepare a vinyl resin, dissolve the resin in a solvent to prepare a resin
solution, dissolve an emulsifier in the resin solution, and add water
thereto to cause phase-transfer emulsification.

[0101] The process (a) is simple and is able to prepare fine resin
particle in the form of liquid dispersion. Therefore, the process (a) can
be easily applicable to toner manufacturing process.

[0102] In the process (a), the resulting fine vinyl resin particles may be
given dispersion stability by containing a dispersion stabilizer in an
aqueous medium within which the polymerization takes place and/or
including a monomer which are capable of giving dispersion stability to
the fine resin particles (i.e., reactive emulsifier) in the mixture of
monomers. In the absence of a dispersion stabilizer and/or a reactive
emulsifier, the vinyl resin may not be formed into fine particles. Even
in a case in which the vinyl resin can be formed into fine particles, the
fine particles are likely to aggregate when stored due to their poor
storage stability or to cause aggregation or coalescence of the core
particles, resulting in formation of toner particles with nonuniform
shapes and surface conditions.

[0104] In preparing the fine resin particles, a chain transfer agent may
be used for adjusting their molecular weight. Usable chain transfer
agents include alkyl-mercaptan-type chain transfer agents having a
hydrocarbon group having a carbon number of 3 or more. Specific examples
of such hydrophobic alkyl-mercaptan-type chain transfer agents having a
hydrocarbon group having a carbon number of 3 or more include, but are
not limited to, butanethiol, octanethiol, decanethiol, dodecanethiol,
hexadecanethiol, octadecanethiol, cyclohexyl mercaptan, thiophenol, octyl
thioglycolate, octyl 2-mercaptopropionate, octyl 3-mercaptopropionate,
mercaptopropionic acid 2-ethylhexyl ester, octanoic acid 2-mercaptoethyl
ester, 1,8-dimercapto-3,6-dioxaoctane, decane trithiol, and dodecyl
mercaptan. Two or more of these hydrophobic chain transfer agents can be
used in combination.

[0105] In some embodiments, the chain transfer agent in an amount of 0.01
to 30 parts by weight, or 0.1 to 25 parts by weight, based on 100 parts
by weight of the monomers is added for adjusting molecular weight of the
resulting copolymer. When the added amount of the chain transfer agent
falls below 0.01 parts by weight, gelation is caused during the
polymerization or the molecular weight of the copolymer becomes so large
that fixability of the toner deteriorates. When the added amount of the
chain transfer agent exceeds 30 parts by weight, the unreacted chain
transfer agents remains or the molecular weight of the copolymer becomes
so small that the toner contaminates peripheral members.

[0106] According to some embodiments, the vinyl resin has a weight average
molecular weight of 3,000 to 500,000, 5,000 to 500,000, or 6,000 to
450,000. When the weight average molecular weight falls below 3,000, the
vinyl resin is so weak in physical strength that the surface condition of
the toner is easily altered depending on toner usage conditions. For
example, the toner may significantly change its chargeability or
contaminate peripheral members accompanied by deterioration of image
quality. When the weight average molecular weight exceeds 500,000, it
means that the vinyl resin is deficient in the number of molecular chain
terminals. The molecular chains of the vinyl resin become less able to
intertangle with molecular chains of the core particles, which means that
the vinyl resin particles are prevented from adhering to the core
particles.

[0107] According to some embodiments, the vinyl resin has a glass
transition temperature (Tg) within a range of 45 to 100° C., 60 to
90° C., or 70 to 90° C. When Tg falls below 45° C.,
the resulting toner may cause blocking when stored in a high-temperature
condition.

[0108] In some embodiments, the glass transition temperature (Tg) of the
vinyl resin is greater than the melting point (Tm2) of the toner, i.e.,
Tm2<Tg is satisfied. When Tm2<Tg is satisfied, the glass transition
temperature of the vinyl resin is not significantly reduced even when the
vinyl resin is plasticized by moisture in the air when stored in a
high-temperature and high-humidity condition. Also, the resulting toner
is not significantly degraded even when exposed to frictional forces in
one-component developing processes. When Tm2<Tg is satisfied, the
toner is also fixable at low temperatures.

[0109] According to some embodiments, when the toner is subjected to first
and second heating processes by a differential scanning calorimeter, the
ratio (Tsh2nd/Tsh1st) of the second shoulder temperature (Tsh2nd) of the
second peak of melting heat observed in the second heating process to the
first shoulder temperature (Tsh1st) of the first peak of melting heat
observed in the first heating process is within a range of 0.90 to 1.10,
i.e., 0.90≦Tsh2nd/Tsh1st≦1.10 is satisfied.

[0110] The shoulder temperatures (Tsh1st and Tsh2nd) of the peaks of
melting heat can be measured by a differential scanning calorimeter such
as TA-60WS or DSC-60 (both from Shimadzu Corporation) as follows. Contain
5.0 mg of a toner in an aluminum sample container and set the container
to a holder unit in an electric furnace. In nitrogen atmosphere, heat the
sample from 0° C. to 150° C. at a heating rate of
10° C./min to obtain a first DSC curve. Subsequently, cool the
sample from 150° C. to 0° C. at a cooling rate of
10° C./min and further heat the sample to 150° C. at a
heating rate of 10° C./min to obtain a second DSC curve. Designate
an endothermic peak temperature observed in the first DSC curve as Tm1st
and an endothermic peak temperature observed in the second DSC curve as
Tm2nd. In a case in which multiple endothermic peaks are observed in each
DSC curve, select a peak which is expressing the maximum endothermic
quantity. Determine an intersection of the lower-temperature-side
baseline of each DSC curve with the tangent line of the
lower-temperature-side slope of each selected endothermic peak. Designate
the temperatures at the intersections in the first and second DSC curves
as Tsh1st and Tsh2nd, respectively.

[0111] According to some embodiments, the toner satisfies the following
inequations: G'(70)≧1.0×103,
5.0×103<G'(70)<5.0×106, or
5.0×104<G'(70)<5.0×105, wherein G'(70) (Pa)
represents a storage elastic modulus of the toner at 70° C.
According to some embodiments, the toner satisfies the following
inequations: G'(160)≦5.0×106,
1.0×101<G'(160)<5.0×105, or
1.0×103<G'(160)<1.0×104, wherein G'(160) (Pa)
represents a storage elastic modulus of the toner at 160° C. When
storage elastic modulus is within the above-described ranges, the toner
provides high fixation strength and hot offset resistance.

[0112] Storage elastic modulus can be adjusted by varying the mixing ratio
of crystalline and amorphous resins or molecular weight of the resins.
For example, as the ratio of the crystalline resin increases, G'(160)
increases.

[0113] Storage elastic modulus can be measured by a dynamic
viscoelasticity measuring device such as ARES (from TA Instruments) as
follows.

[0114] Cast a sample into a pellet having a diameter of 8 mm and a
thickness of 1 to 2 mm. Fix the pellet to parallel plates having a
diameter of 8 mm and stabilized at 40° C. Subject the pellet to a
measurement by heating the pellet to 200° C. at a heating rate of
2.0° C./min while setting the frequency to 1 Hz (6.28 rad/s) and
the amount of strain to 0.1% (under strain control mode).

[0117] The toner may further include a release agent dispersant. As the
release agent dispersant, the following materials may be used: a polymer
or oligomer comprised of a block unit having high compatibility with
release agent and another block unit having high compatibility with
binder resin; a polymer or oligomer comprised of a unit having high
compatibility with release agent and another unit having high
compatibility with binder resin, one of them is grafted to the other; a
copolymer of an unsaturated hydrocarbon (e.g., ethylene, propylene,
butene, styrene, α-styrene) with an α,β-unsaturated
carboxylic acid or an ester or anhydride thereof (e.g., acrylic acid,
methacrylic acid, methyl methacrylate, maleic acid, maleic anhydride,
itaconic acid, itaconic anhydride); and a block or graft copolymer of a
vinyl resin with a polyester.

[0119] Additionally, fine particles of polymers may also be used as the
external additive. Usable polymers include, for example, polystyrene that
can be obtained by soap-free emulsion polymerization, suspension
polymerization, or dispersion polymerization; polycondensation resins
such as copolymers of methacrylates and acrylates, or silicone,
benzoguanamine, or nylon resin; and thermosetting resins.

[0120] The external additives may be treated with a surface treatment
agent so as to improve hydrophobicity. The hydrophobized external
additive can prevent deterioration of fluidity and chargeability of the
toner in high-humidity conditions. Usable surface treatment agents
include, but are not limited to, silane coupling agents, silylation
agents, silane coupling agents having a fluorinated alkyl group, organic
titanate coupling agents, aluminum coupling agents, silicone oils, and
modified silicone oils.

[0121] The toner may further include a cleanability improving agent so as
to be easily removable from a photoreceptor or a primary transfer medium
when remaining thereon after image transfer. Specific examples of usable
cleanability improving agents include, but are not limited to, metal
salts of fatty acids (e.g., zinc stearate, calcium stearate) and fine
particles of polymers which can be prepared by soap-free emulsion
polymerization (e.g., polymethyl methacrylate, polystyrene). In some
embodiments, the fine particles of polymers have a narrow size
distribution and a volume average particle diameter of 0.01 to 1 μm.

[0122] In accordance with some embodiments, the toner is prepared by the
steps of: dissolving or dispersing constituents of the core particle,
such as a binder resin, a colorant, a release agent, etc., in an organic
solvent to prepare an oil phase; dispersing the oil phase in an aqueous
medium to prepare a dispersion liquid containing droplets of the oil
phase (hereinafter "core droplets" for the sake of simplicity); mixing
the dispersion liquid containing core droplets with another dispersion
liquid containing fine resin particles so that the fine resin particles
are adhered to the surfaces of the core droplets; and removing the
organic solvent from the core droplets to obtain core particles having
the projections at their surfaces.

[0123] Usable organic solvents include volatile solvents having a boiling
point less than 100° C. that are easily removable in succeeding
processes. Specific examples of such organic solvents include, but are
not limited to, toluene, xylene, benzene, carbon tetrachloride, methylene
chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene,
chloroform, monochlorobenzene, dichloroethylidene, methyl acetate, ethyl
acetate, methyl ethyl ketone, and methyl isobutyl ketone. Two or more of
these solvents can be used in combination. In some embodiments, ester
solvents such as methyl acetate and ethyl acetate, aromatic solvents such
as toluene and xylene, and halogenated hydrocarbons such as
1,2-dichloroethane, chloroform, and carbon tetrachloride are used. The
binder resin and colorant may be dissolved or dispersed in either a
single organic solvent together or separate organic solvents. In the
latter case, the separate organic solvents may be either identical or
different. When the separate organic solvents are identical, succeeding
solvent removing processes become much simpler. According to some
embodiments, either single or mixture solvents which dissolve the binder
resin poorly dissolve the release agent.

[0124] A solution or dispersion of the binder resin may have a resin
concentration of 40 to 80%. When the resin concentration is too high, the
solution or dispersion gets too viscous to be handled with ease. When the
resin concentration is too low, the yield of core particles decreases
while the waste solvent increases. In a case in which the binder resin
comprises a crystalline polyester and a modified polyester having an
isocyanate group on its terminal, the crystalline polyester and the
modified polyester may be dissolved or dispersed in either a single
organic solvent together or separate organic solvents. The latter case
more takes into account solubility and viscosity of each polyester.

[0125] The aqueous media may be, for example, water alone or a mixture of
water and a water-miscible solvent. Specific examples of usable
water-miscible solvents include, but are not limited to, alcohols (e.g.,
methanol, isopropanol, ethylene glycol), dimethylformamide,
tetrahydrofuran, cellosolves (e.g., methyl cellosolve), and lower ketones
(e.g., acetone, methyl ethyl ketone). According to an embodiment, the
used amount of the aqueous medium is 50 to 2,000 parts by weight, or 100
to 1,000 parts by weight, based on 100 parts by weight of the core
particles.

[0126] The aqueous medium may contain an inorganic dispersant or an
organic resin particle for the purpose of stably dispersing the oil phase
therein and narrowing particle size distribution of the core droplets.
Specific examples of usable inorganic dispersants include, but are not
limited to, tricalcium phosphate, calcium carbonate, titanium oxide,
colloidal silica, and hydroxyapatite. The organic resin particle may be
prepared from a resin capable of forming an aqueous dispersion thereof.
Such resins include thermoplastic and thermosetting resins such as vinyl
resin, polyurethane resin, epoxy resin, polyester resin, polyamide resin,
polyimide resin, silicone resin, phenol resin, melamine resin, urea
resin, aniline resin, ionomer resin, and polycarbonate resin. Two or more
of these resins can be used in combination. Among the above resins, a
vinyl resin, a polyurethane resin, an epoxy resin, a polyester resin, or
a combination thereof are much easier to form an aqueous dispersion of
fine spherical particles thereof.

[0130] Any type of disperser can be used, such as a low-speed shearing
disperser, a high-speed shearing disperser, a frictional disperser, a
high-pressure jet disperser, or an ultrasonic disperser. A high-speed
shearing disperser may be used while setting a revolution to 1,000 to
30,000 rpm, or 5,000 to 20,000 rpm. The dispersing temperature may be 0
to 150° C. (under pressure) or 20 to 80° C.

[0131] In the step of dissolving or dispersing constituents of the core
particle, such as a binder resin, a colorant, a release agent, etc., in
an organic solvent to prepare an oil phase, the constituents are
gradually added to the organic solvent while the organic solvent is
agitated.

[0132] Constituent materials which are poorly soluble in the organic
solvent (e.g., pigments, release agents, charge controlling agents) may
be previously ground into fine particles before being added to the
organic solvent.

[0133] Colorants, release agents, and charge controlling agents may be
previously combined with a resin to be formed into a master batch.

[0134] Alternatively, colorants, release agents, and charge controlling
agents, optionally along with a dispersing auxiliary agent, may be
previously combined with a resin in a wet condition to be formed into a
wet master batch.

[0135] Constituent materials which are meltable at temperatures below the
boiling point of the organic solvent may be previously formed into fine
crystal grain by being dissolved in the organic solvent, optionally along
with a dispersing auxiliary agent, while the organic solvent is agitated
and heated, and subsequently cooled while the organic solvent is agitated
or sheared.

[0136] After having been dispersed in the organic solvent along with the
binder resin by any of the above procedures, the colorant, release agent,
and/or charge controlling agent may be further subject to a dispersion
treatment by a disperser, such as a bead mill and a disc mill.

[0137] In the step of dispersing the oil phase in an aqueous medium to
prepare a dispersion liquid containing core droplets, any type of
disperser an be used, such as a low-speed shearing disperser, a
high-speed shearing disperser, a frictional disperser, a high-pressure
jet disperser, or an ultrasonic disperser. A high-speed shearing
disperser can produce droplets having a particle diameter of 2 to 20
μm. A high-speed shearing disperser may be used while setting a
revolution to 1,000 to 30,000 rpm, or 5,000 to 20,000 rpm. The dispersing
time may be 0.1 to 5 minutes when the used disperser is a batch type.
When the dispersing time exceeds 5 minutes, the core droplets are
excessively dispersed. As a result, undesirable ultrafine droplets may
remain dispersed or get aggregated or coarsened. The dispersing
temperature may be 0 to 150° C. or 20 to 80° C. When the
dispersing temperature exceeds 150° C., molecules of the dispersed
materials get active and therefore core droplets get aggregated or
coarsened. When the dispersing temperature falls below 0° C., the
dispersion liquid gets so viscous that a greater amount of energy is
needed, which results in deterioration of manufacturing efficiency.

[0138] The aqueous medium may contain a surfactant. Specific examples of
usable surfactants include those usable for preparing a dispersion liquid
of the organic resin particle described above. For example, disulfonates
having a relatively high HLB, which are able to effectively disperse core
droplets, can be used. In some embodiments, the content of the surfactant
in the aqueous medium is 1 to 10% by weight, 2 to 8% by weight, or 3 to
7% by weight. When the content exceeds 10% by weight, the core droplets
get too small or take a reverse micelle structure. As a result, the
dispersion liquid gets unstable and the core droplets get coarsened. When
the content falls below 1% by weight, it is difficult to stably disperse
the core droplets and the core droplets get coarsened.

[0139] In the dispersion liquid thus prepared, the core droplets are kept
stably dispersed so long as the dispersion liquid is under agitation.
While the core droplets are stably dispersed, a dispersion liquid
containing fine vinyl resin particles is mixed therein so that the fine
vinyl resin particle are brought into adhesion to the core droplets.

[0140] The shape of the projections can be controlled by, for example,
varying the time period during which the dispersion liquid containing
fine vinyl resin particles is mixed in the dispersion liquid containing
core droplets, the concentration and/or used amount of the dispersion
liquid containing fine vinyl resin particles, the temperature at which
the projection is formed, or Dv/Dn (particle size distribution) of the
fine vinyl resin particles.

[0141] In some embodiments, the dispersion liquid containing fine vinyl
resin particles is mixed in the dispersion liquid containing core
droplets over a period of 30 seconds or more. When the time period is
less than 30 seconds, the dispersion system is so rapidly changed that
the fine vinyl resin particles are brought into self-aggregation or
nonuniform adhesion to the core droplets. When the time period is too
long, for example, exceeds 60 minutes, manufacturing efficiency
deteriorates.

[0142] The dispersion liquid containing fine vinyl resin particles may be
diluted or condensed for adjusting the resin concentration before being
mixed with the dispersion liquid containing core droplets. In some
embodiments, the concentration of the fine vinyl resin particles in the
dispersion liquid is 5 to 30% by weight or 8 to 26% by weight. When the
concentration of the fine vinyl resin particles is less than 5% by
weight, the concentration of the organic solvent greatly changes upon
mixing in the dispersion liquid containing core droplets. As a result,
the fine vinyl resin particles are brought into adhesion to the core
droplets only slightly, resulting in deterioration of surface coverage of
core particle with projections. When the concentration of the fine vinyl
resin particles is greater than 30% by weight, the fine vinyl resin
particles are non-uniformly dispersed in the mixed dispersion liquid and
brought into non-uniform adhesion to the core droplets. The resulting
projections may not meet the requirement of standard deviation of the
lengths of their long sides.

[0143] The surface coverage of core particle with projections can be
controlled by varying the amount of the dispersion liquid containing fine
vinyl resin particles to be mixed in the dispersion liquid containing
core droplets.

[0144] The fine vinyl resin particles are brought into adhesion to the
core droplets with sufficient strength. This is because the core droplets
are flexible enough to form a sufficient contact area between the fine
vinyl resin particles. This is also because the fine vinyl resin
particles are swelled or dissolved by the organic solvent and thus
express adhesive property. Thus, the core droplets should include a
certain amount of organic solvent. In some embodiments, the content of
the organic solvent in the dispersion liquid containing core droplets is
10 to 70% by weight, 30 to 60% by weight, or 40 to 55% by weight, based
on solid contents (e.g., resins, colorants, release agents, charge
controlling agents). When the content of the organic solvent exceeds 70%
by weight, efficiency and stability in manufacturing core particles
deteriorate, for example, the core droplets may self-aggregate. When the
content of the organic solvent falls below 10% by weight, the fine vinyl
resin particles may be adhered to the core droplets with only a weak
adhesion force. In a case in which a desired organic solvent
concentration for bringing the fine vinyl resin particles to adhesion to
the core droplets is lower than that for forming the core droplets, a
part of the organic solvent may be removed after the core droplets have
been formed and the residual organic solvent may be completely removed
after the fine vinyl resin particles have been brought into adhesion to
the core droplets.

[0145] In some embodiments, the fine vinyl resin particles are brought
into adhesion to the core droplets at a temperature within a range of 10
to 45° C., or 20 to 30° C. When the temperature is higher
than 45° C., energy consumption and environmental load undesirably
increase in the manufacturing process. Moreover, the fine vinyl resin
particles get coarsened and the resulting projections may not meet the
requirement of the average length and standard deviation of their long
sides. When the temperature is lower than 10° C., the fine vinyl
resin particles are brought into adhesion to the core droplets only
slightly, resulting in deterioration of surface coverage of core particle
with projections.

[0146] As an alternative for the above procedure, the fine resin particles
can be directly added to the aqueous medium before the core droplets are
formed therein.

[0147] In some embodiments, the fine resin particles account for 1 to 20%
by weight, 3 to 15% by weight, or 5 to 10% by weight, of the toner. When
the content of the fine resin particles falls below 1% by weight of the
toner, the projections cannot express their effect. When the content of
the fine resin particles exceeds 20% by weight of the toner, excessive
fine resin particles are weakly adhered to the core particles and the
resulting toner cause filming problem. The content of the fine resin
particles in the toner can be determined from the composition of raw
materials.

[0148] As an alternative for the above procedures, the fine resin
particles and the core particles can be directly mixed so that they are
mechanically adhered to each other.

[0149] According to some embodiments, the ratio (Dv/Dn) of the volume
average particle diameter (Dv) to the number average particle diameter
(Dn) of the fine resin particles is less than 1.25, or less than 1.12, in
view of a desired standard deviation of the long sides of the resulting
projections.

[0150] In some embodiments, the volume average particle diameter (Dv) of
the fine resin particles is 50 to 200 nm, 60 to 150 nm, or 70 to 140 nm.
When Dv falls below 50 nm or exceeds 200 nm, it may be difficult to
uniformly cover the core particles with such fine resin particles.

[0151] The organic solvent is removed from the resulting dispersion liquid
to obtain core particles by, for example, gradually heating the
dispersion liquid under normal or reduced pressures to completely
evaporate the organic solvent.

[0152] In a case in which a modified polyester having an isocyanate group
on its terminal ("polyester prepolymer") in combination with an amine
reactive with the modified polyester are included in the constituents,
for the purpose of introducing a modified polyester having urethane
and/or urea bonds into the toner, the amine may be mixed in either the
oil phase before the oil phase is dispersed in the aqueous medium or the
aqueous medium. According to some embodiments, the isocyanate group in
the polyester prepolymer reacts with the amine over a period of 1 minute
to 40 hours, or 1 to 24 hours. The dispersing temperature may be 0 to
150° C. or 20 to 98° C.

[0153] The resulting toner particles can be isolated as follows.

[0154] First, the resulting dispersion liquid is separated into solid and
liquid by means of a centrifugal separator or filter press. The solid,
i.e., a toner cake, is redispersed in ion-exchange water at normal
temperature to about 40° C. The pH of the dispersion may be
controlled by acids and bases, if needed. This procedure is repeated
several times until impurities and surfactants are removed from the toner
cake. The toner cake is then dried by a flash drier, a circulating drier,
a reduced-pressure drier, or a vibrating fluid bed drier. Undesired
ultrafine particles may be removed by a centrifugal separator during the
drying process, or alternatively, by a classifier after the drying
process.

[0155] The toner particles may be mixed with heterogeneous particles, such
as a charge controlling agent and a fluidizer, upon application of
mechanical impulsive force, so that the heterogeneous particles are fixed
or fused on the surfaces of the toner particles. Mechanical impulsive
force can be applied by, for example, agitating the mixture of toner and
heterogeneous particles with blades rotating at a high speed, or
accelerating the mixture in a high-speed airflow to allow the toner and
heterogeneous particles collide with a collision plate. Such a treatment
can be performed by ONG MILL (from Hosokawa Micron Co., Ltd.), a modified
I-TYPE MILL in which the pulverizing air pressure is reduced (from Nippon
Pneumatic Mfg. Co., Ltd.), HYBRIDIZATION SYSTEM (from Nara Machine Co.,
Ltd.), KRYPTON SYSTEM (from Kawasaki Heavy Industries, Ltd.), or an
automatic mortar.

[0156] According to some embodiments, the toner has a volume average
particle diameter within a range of 3 to 9 μm, 4 to 8 μm, or 4 to 7
μm, in view of chargeability. When the volume average particle
diameter falls below 3 μm, adhesive force of the toner relatively
increases and operability of the toner in an electric field deteriorates.
When the volume average particle diameter exceeds 9 μm, image quality,
such as thin line reproducibility, deteriorates.

[0157] In some embodiments, the ratio of the volume average particle
diameter to the number average particle diameter of the toner is 1.25 or
less, 1.20 or less, or 1.17 or less. When the ratio exceeds 1.25,
particle size distribution of the toner is so wide that the resulting
projections may be varied in size. As coarse and ultrafine toner
particles are gradually consumed in a developing device, the average
particle size of toner particles remaining in the developing device is
gradually varied. Although optimal conditions for developing images
depend on the average particle size of toner particles, the developing
device keeps developing images without changing any condition. As a
result, undesirable phenomena occurs, such as insufficient charging of
toner, extreme increase or decrease in toner conveyance quantity, toner
clogging, and toner spilling.

[0158] Particle size distribution of toner can be measured by instruments
such as COULTER COUNTER TA-II and COULTER MULTISIZER II (both from
Beckman Coulter Inc.) as follows.

[0159] First, add 0.1 to 5 ml of a surfactant (e.g., an alkylbenzene
sulfonate) to 100 to 150 ml of an electrolyte. The electrolyte is an
about 1% NaCl aqueous solution prepared from the first grade sodium
chloride, such as a commercial product ISOTON-II (available from Beckman
Coulter, Inc.) Next, add 2 to 20 mg of a sample (toner particles) to the
electrolyte. Subject the electrolyte, in which the sample is suspended,
to a dispersion treatment with an ultrasonic disperser for about 1 to 3
minutes, and subsequently to a measurement of volume and number
distributions of the sample with the above instrument having an aperture
of 100 μm. Volume average particle diameter (D4) and number average
particle diameter (D1) are calculated from the volume and number
distributions, respectively, measured above.

[0160] The following 13 channels are used so that particles having a
particle diameter not less than 2.00 μm but less than 40.30 μm are
to be measured: not less than 2.00 μm but less than 2.52 μm; not
less than 2.52 μm but less than 3.17 μm; not less than 3.17 μm
but less than 4.00 μm; not less than 4.00 μm but less than 5.04
μm; not less than 5.04 μm but less than 6.35 μm; not less than
6.35 μm but less than 8.00 μm; not less than 8.00 μm but less
than 10.08 μm; not less than 10.08 μm but less than 12.70 μm;
not less than 12.70 μm but less than 16.00 μm; not less than 16.00
μm but less than 20.20 μm; not less than 20.20 μm but less than
25.40 μm; not less than 25.40 μm but less than 32.00 μm; and not
less than 32.00 μm but less than 40.30 μm.

[0161] In some embodiments, the toner has an average circularity of 0.930
or more, 0.950 or more, or 0.970 or more. When the average circularity
falls below 0.930, fluidity of the toner deteriorates and therefore
developing and transfer efficiencies also deteriorate.

[0162] The average circularity can be measured by a flow-type particle
image analyzer FPIA-2000 (from Sysmex Corporation) as follows. Add 0.1 to
0.5 ml of a surfactant (e.g., an alkylbenzene sulfonate) to 100 to 150 ml
of water from which solid impurities have been removed, and further add
0.1 to 0.5 g of a sample thereto. Subject the resulting suspension to a
dispersion treatment with an ultrasonic disperser for about 1 to 3
minutes. Subject the suspension containing 3,000 to 10,000 particles per
micro-liter to a measurement of shape distribution of the sample with
above instrument.

[0163] A process cartridge according to an embodiment includes at least an
electrostatic latent image bearing member adapted to bear an
electrostatic latent image and a developing device adapted to develop the
electrostatic latent image into a toner image with the toner according to
an embodiment.

[0164]FIG. 2 is a schematic view of a process cartridge according to an
embodiment.

[0165] The process cartridge illustrated in FIG. 2 includes an
electrostatic latent image bearing member 3K, an electrostatic latent
image bearing member charger 7K, a charging member 10K adapted to
recharge residual toner particles remaining on the electrostatic latent
image bearing member 3K after image transfer, and a developing device
40K. The process cartridge is detachably attachable to image forming
apparatuses such as copiers and printers.

[0166] During normal operations, the electrostatic latent image bearing
member 3K is driven to rotate at a predetermined peripheral speed. A
peripheral surface of the electrostatic latent image bearing member 3K is
uniformly charged to a predetermined positive or negative potential by
the charger 7K and then irradiated with light L by means of slit exposure
or laser beam scanning while the electrostatic latent image bearing
member 3K is rotating. As a result, electrostatic latent images are
sequentially formed on the peripheral surface of the electrostatic latent
image bearing member 3K. The electrostatic latent images are developed
into toner images by the developing device 40K. The toner images are
sequentially transferred onto a transfer material 61 fed from a paper
feed part to a gap between the electrostatic latent image bearing member
3K and a transfer device 66K in synchronization with rotation of the
electrostatic latent image bearing member 3K.

[0167] The transfer material 61 having the toner image thereon is
separated from the peripheral surface of the electrostatic latent image
bearing member 3K and introduced into a fixing device so that the toner
image is fixed thereon. The transfer material 61 having the fixed toner
image is discharged from the image forming apparatus as a copy.

[0168] Residual toner particles remaining on the peripheral surface of the
electrostatic latent image bearing member 3K after image transfer are
recharged by the charging member 10K having an elastic part 8K and a
conductive sheet 9K, allowed to pass under the charger 7K, and collected
in the developing device 40 to be recycled.

[0169] The developing device 40K includes a casing 41K and a developing
roller 42K. A part of the peripheral surface of the developing roller 42K
is exposed from an aperture provided on the casing 41K.

[0170] The shaft of the developing roller 42K is protruding from
longitudinal ends of the developing roller 42K. Each end of the shaft is
rotatably supported by a bearing.

[0171] The casing 41K contains toner particles. An agitator 43K is driven
to rotate so as to feed the toner particles from a right side to a left
side in FIG. 2.

[0172] A toner supply roller 44K is disposed on a left side of the
agitator 43K in FIG. 2. The toner supply roller 44K is driven to rotate
counterclockwise in FIG. 2. The toner supply roller 44K is comprised of
an elastic foam, such as sponge, which can effectively catch toner
particles fed from the agitator 43K.

[0173] Toner particles caught by the toner supply roller 44K are supplied
to the developing roller 42K at a position where the toner supply roller
44K contacts the developing roller 42K.

[0174] The toner particles borne on the developing roller 42K are then
passed through a position where the developing roller 42K contacts a
regulation blade 45K as the developing roller 42K rotates
counterclockwise in FIG. 2. At the position, the regulation blade 45
regulates the thickness of the layer of the toner particles while
frictionally charging the toner particles. The toner particles are then
conveyed to a developing area where the developing roller 42K is facing
the electrostatic latent image bearing member 3K.

[0175] The charging member 10K is adapted to recharge residual toner
particles remaining on the electrostatic latent image bearing member 3K
after image transfer. The charging member 10K is conductive. If the
charging member 10K is insulative, toner particles may undesirably adhere
thereto due to the occurrence of charge up.

[0176] According to some embodiments, the charging member 10K is comprised
of a sheet of nylon, PTFE, PVDF, or urethane. PTFE and PVD are
advantageous in view of toner charging ability.

[0177] According to some embodiments, the charging member 10K has a
surface resistivity of 102 to 108 Ω/sq and a volume
resistivity of 101 to 106 Ω/sq.

[0178] The charging member 10K may be in the form of either roller, brush,
or sheet. When the charging member 10K is in the form of sheet, toner
particles adhered thereto are most easily removable.

[0179] According to some embodiments, the charging member 10K is supplied
with a voltage of -1.4 to 0 kV.

[0180] When the charging member 10K is in the form of sheet, the thickness
of the sheet may be 0.05 to 0.5 mm in view of the contact pressure with
the electrostatic latent image bearing member 3K.

[0181] Additionally, a nip where the sheet is in contact with the
electrostatic latent image bearing member 3K has width of 1 to 10 mm in
view of the contact time period for charging toner particles.

[0182] An image forming apparatus according to an embodiment includes a
latent image bearing member, a charger adapted to uniformly charge a
surface of the latent image bearing member, an irradiator adapted to emit
light to the charged surface of the latent image bearing member based on
image information to write an electrostatic latent image thereon, a
developing device adapted to develop the electrostatic latent image into
a toner image with a toner according to an embodiment, a transfer device
adapted to transfer the toner image from the latent image bearing member
onto a transfer material, and a fixing device adapted to fix the toner
image on the transfer material. The image forming apparatus may
optionally include a neutralizer, a cleaner, a recycler, and a
controller.

[0183] An image forming method according to an embodiment includes the
steps of uniformly charging a surface of a latent image bearing member,
irradiating the charged surface of the latent image bearing member with
light based on image information to write an electrostatic latent image
thereon, developing the electrostatic latent image into a toner image
with a toner according to an embodiments borne on a developer bearing
member, transferring the toner image from the latent image bearing member
onto a transfer material, and fixing the toner image on the transfer
material. The image forming method may optionally include the steps of
neutralizing, cleaning, recycling, and controlling.

[0184] An electrostatic latent image is formed by uniformly charging a
surface of the latent image bearing member by the charger and irradiating
the charged surface with light containing image information.

[0185] A toner image is formed by forming a toner layer on a developing
roller, serving as the developer bearing member, and bringing the toner
layer on the developing roller into contact with the electrostatic latent
image on the latent image bearing member.

[0186] Toner particles are agitated by an agitator and mechanically
supplied to a developer supply member.

[0187] The toner particles supplied from the developer supply member and
accumulated on the developer bearing member are allowed to pass through a
developer layer regulator disposed in contact with the developer bearing
member so that a uniform thin layer of the toner particles is formed
while the toner particles are frictionally charged.

[0188] The electrostatic latent image formed on the latent image bearing
member is developed into a toner image by being supplied with the charged
toner particles in a developing area.

[0189] The toner image is transferred from the latent image bearing member
onto a transfer material by charging the latent image bearing member by
the transfer device such as a transfer charger.

[0190] The toner image is then fixed on the transfer material. Each
single-color toner image may be independently fixed on a transfer
material, or alternatively, a composite toner image including a plurality
of color toner images may be fixed on a transfer material at once.

[0191] The fixing device may have functions of heating and pressing.

[0192] For example, the fixing device may include a combination of a
heating roller and a pressing roller, or a combination of a heating
roller, a pressing roller, and an endless belt.

[0193] In some embodiments, the heating member is heated to a temperature
of 80 to 200° C.

[0194]FIG. 3 is a schematic view of an image forming apparatus according
to an embodiment.

[0197] This image forming apparatus is a tandem image forming apparatus
including multiple latent image bearing members arranged in tandem in the
direction of movement of a surface moving member.

[0198] In particular, this image forming apparatus includes four
photoreceptors 1Y, 1C, 1M, and 1K each serving as the latent image
bearing member. The photoreceptors may have either a drum-like shape as
illustrated in FIG. 2 or a belt-like shape.

[0199] The photoreceptors 1Y, 1C, 1M, and 1K are driven to rotate in the
direction indicated by arrows in FIG. 3 while contacting an intermediate
transfer belt 10 serving as the surface moving member.

[0200] Each of the photoreceptors 1Y, 1C, 1M, and 1K is comprised of, from
the innermost side thereof, a relatively thin cylindrical conductive
support, a photosensitive layer, and a protective layer. An intermediate
layer may be optionally formed between the photosensitive layer and the
protective layer.

[0201]FIG. 4 is a schematic view of each image forming parts 2Y, 2C, 2M,
and 2K.

[0202] Since the image forming parts 2Y, 2C, 2M, and 2K have the same
configuration, additional characters Y, C, M, and K are omitted from the
reference numerals in FIG. 4.

[0203] Around the photoreceptor 1, a charger 3, a developing device 5, a
transfer device 6, and a cleaner 7 are disposed in this order. The
transfer device 6 is adapted to transfer a toner image from the
photoreceptor 1 onto the intermediate transfer belt 10. The cleaner 7 is
adapted to remove residual toner particles remaining on the photoreceptor
1 without being transferred.

[0204] Around the photoreceptor 1, a space is provided between the charger
3 and the developing device 5. The space allows light emitted from an
irradiator 4 to reach a charged surface of the photoreceptor 1 so that an
electrostatic latent image is formed on the photoreceptor 1 based on
image information.

[0205] The charger 3 charges a surface of the photoreceptor 1 to a
negative polarity.

[0206] According to an embodiment, the charger 3 is in the form of roller
("charging roller").

[0207] The charging roller is brought into contact with or close to a
surface of the photoreceptor 1 and supplied with a negative bias for
charging the surface of the photoreceptor 1.

[0208] For example, the charging roller may be supplied with a direct
current charging bias for charging the surface of the photoreceptor 1 to
-500 V.

[0209] The charging bias may be a direct current bias overlapped with an
alternating current bias.

[0210] The charger 3 may be equipped with a cleaning brush that cleans the
surface of the charging roller.

[0211] Each axial end part of the charging roller may be wrapped around
with a thin tape and brought into contact with the surface of the
photoreceptor 1.

[0212] In this case, the surface of the charging roller is brought close
to the surface of the photoreceptor 1 while forming a gap therebetween.
The gap has a distance equivalent to the thickness of the tape. Upon
application of a charging bias to the charging roller, electric discharge
occurs in the gap. As a result, the surface of the photoreceptor 1 is
charged.

[0213] The charged surface of the photoreceptor 1 is then irradiated with
light emitted from the irradiator 4. As a result, an electrostatic latent
image is formed on the photoreceptor 1.

[0214] The irradiator 4 writes an electrostatic latent image on the
photoreceptor 1 based on image information of each color.

[0215] The irradiator 4 may employ either a laser method or another method
using an LED array and an imaging device.

[0217] The developing roller 5a conveys the toner particles to a
developing area where the developing roller 5a is facing the
photoreceptor 1.

[0218] In the developing area, the surface of the developing roller 5a
moves in the same direction as the surface of the photoreceptor 1 moves
at a higher linear speed than the photoreceptor 1.

[0219] Toner particles carried on the developing roller 5a are supplied to
the surface of the photoreceptor 1 while the developing roller 5a is
abrasively contacting the surface of the photoreceptor 1. The developing
roller 5a is supplied with a developing bias of -300 V from a power
source. As a result, a developing electric field is formed in the
developing area.

[0220] Toner particles carried on the developing roller 5a are
electrostatically attracted to the electrostatic latent image on the
photoreceptor 1.

[0221] Thus, the electrostatic latent image on the photoreceptor 1 is
developed into a toner image.

[0222] In the transfer device 6, the intermediate transfer belt 10 is
stretched across three support rollers 11, 12, and 13 and is endlessly
movable in a direction indicated by arrow in FIG. 3.

[0223] Toner images formed on the photoreceptors 1Y, 1C, 1M, and 1K are
electrostatically transferred onto the intermediate transfer belt 10 in
sequence and superimposed on one another.

[0224] The transfer of toner images are performed by respective primary
transfer rollers 14Y, 14C, 14M, and 14K, which cause less toner
scattering than transfer chargers.

[0226] Thus, primary transfer nips are formed between the photoreceptors
1Y, 1C, 1M, and 1K and each portions of the intermediate transfer belt 10
pressed by the primary transfer rollers 14Y, 14C, 14M, and 14K,
respectively.

[0227] Toner images formed on the photoreceptors 1Y, 1C, 1M, and 1K are
transferred onto the intermediate transfer belt 10 by supplying a
positive bias to each of the primary transfer rollers 14Y, 14C, 14M, and
14K.

[0228] Thus, a transfer electric field is formed in each primary transfer
nip. Each toner image formed on the photoreceptor 1Y, 1C, 1M, or 1K is
electrostatically attracted to the intermediate transfer belt 10.

[0231] The collected toner particles are fed from the belt cleaner 15 to a
waste toner tank.

[0232] A secondary transfer roller 16 is in contact with the intermediate
transfer belt 10 at a position where the support roller 13 presses
against the intermediate transfer belt 10.

[0233] Thus, a secondary transfer nip is formed between the secondary
transfer roller 16 and the intermediate transfer belt 10. A sheet of
transfer paper (hereinafter "a transfer paper") is timely fed to the
secondary transfer nip.

[0234] Sheets of transfer paper are stored in a paper feed cassette 20
disposed below the irradiator 4 in FIG. 3. A paper feed roller 21 and a
pair of registration rollers 22 feed sheets to the secondary transfer
nip.

[0235] The toner images superimposed on one another on the intermediate
transfer belt 10 are transferred onto a transfer paper in the secondary
transfer nip at once.

[0236] At the secondary transfer, the secondary transfer roller 16 is
supplied with a positive bias so that a transfer electric field is
formed. The toner images are transferred from the intermediate transfer
belt 10 onto a transfer paper by action of the transfer electric field.

[0237] A heat fixing device 23 is disposed downstream from the secondary
transfer nip relative to the direction of conveyance of the transfer
paper.

[0238] The heat fixing device 23 has a heating roller 23a containing a
heater and a pressing roller 23b.

[0239] The transfer paper having passed through the secondary transfer nip
is sandwiched by the heating and pressing rollers 23a and 23b and
received heat and pressure therefrom. Thus, the toner particles on the
transfer paper are melted and fixed thereon. A discharge roller 24
discharges the transfer paper having the fixed toner image onto a
discharge tray.

[0240] A part of the developing roller 5a, serving as the developer
bearing member, is exposed from an aperture provided on the casing of the
developing device 5.

[0241] In the present embodiment, a one-component developer comprising
toner particles and no carrier particles is used.

[0242] The developing device 5 contains toner particles supplied from any
of the toner bottles 31Y, 31C, 31M, and 31K.

[0244] Therefore, there is no need to replace all the toner bottles 31Y,
31C, 31M, and 31K when only one of them gets out of toner. User can keep
using the remaining toner bottles without unnecessary expense.

[0245]FIG. 5 is a schematic view of the developing device 5 illustrated
in FIG. 4. Toner particles are fed to a nip portion formed between the
developing roller 5a and the developer supply roller 5b while being
agitated by the developer supply roller 5b. In the nip portion, the
developer supply roller 5b and the developing roller 5a move in opposite
directions.

[0246] A regulation blade 5c is disposed in contact with the developing
roller 5a. The regulation blade 5c regulates the amount of toner
particles carried on the developing roller 5a and forms a thin layer of
the toner particles.

[0247] Toner particles are frictionally charged in the nip portion between
the developer supply roller 5b and the developing roller 5a as well as in
the gap between the regulation blade 5c and the developing roller 5a.

[0248]FIG. 6 is a schematic view of a process cartridge according to an
embodiment.

[0249] The process cartridge is detachably attachable to image forming
apparatuses such as copiers and printers.

[0251] Having generally described this invention, further understanding
can be obtained by reference to certain specific examples which are
provided herein for the purpose of illustration only and are not intended
to be limiting. In the descriptions in the following examples, the
numbers represent weight ratios in parts, unless otherwise specified.

[0252] Toners prepared in Examples can be used for either one-component
developers or two-component developers.

Measurement of Lengths of Long Sides of Projections and Surface Coverage

[0253] The lengths of the long sides of projections and surface coverage
of toner with the projections are determined from a SEM (scanning
electron microscopy) image of toner.

[0254]FIG. 7 is an example of a SEM image of a toner particle.
Measurement procedures are described below with reference to FIG. 7.

Surface Coverage of Toner

[0255] Draw two parallel lines each tangent to a toner particle at points
A and B with the distance between the points A and B at the minimum.

[0256] Determine an area of a circle drawn with the midpoint O of the line
segment AB at its center. Determine a total area of projections included
within the circle. Calculate a surface coverage by dividing the total
area of the projections by the area of the circle.

[0257] Subject 100 randomly-selected toner particles to the above
procedure and average the calculated values.

Lengths of Long Sides of Projections

[0258] Subject 100 randomly-selected toner particles to a measurement of
the length of the long side of one projection and average the calculated
values. The area and length of each projection is measured with particle
size distribution measurement analysis software Mac-View from Mountech
Co., Ltd.

[0259] Specifically, draw a line passing the gravity center O' of the
projection and intersecting the outer periphery of the projection at
points a and b with the distance between the points a and b at the
maximum. The line segment ab is regarded as the long side of the
projection.

Measurement of Particle Size Distribution

[0260] Particle size distribution of toner is measured by instruments such
as COULTER COUNTER TA-II or COULTER MULTISIZER II (both from Beckman
Coulter Inc.) as follows.

[0261] First, add 0.1 to 5 ml of a surfactant (e.g., an alkylbenzene
sulfonate) to 100 to 150 ml of an electrolyte. The electrolyte is an
about 1% NaCl aqueous solution prepared from the first grade sodium
chloride, such as a commercial product ISOTON-II (available from Beckman
Coulter, Inc.). Next, add 2 to 20 mg of a sample (toner particles) to the
electrolyte. Subject the electrolyte, in which the sample is suspended,
to a dispersion treatment with an ultrasonic disperser for about 1 to 3
minutes, and subsequently to a measurement of volume and number
distributions of the sample with the above instrument having an aperture
of 100 μm. Volume average particle diameter (Dv) and number average
particle diameter (Dn) are calculated from the volume and number
distributions, respectively, measured above.

[0262] The following 13 channels are used so that particles having a
particle diameter not less than 2.00 μm but less than 40.30 μm are
to be measured: not less than 2.00 μm but less than 2.52 μm; not
less than 2.52 μm but less than 3.17 μm; not less than 3.17 μm
but less than 4.00 μm; not less than 4.00 μm but less than 5.04
μm; not less than 5.04 μm but less than 6.35 μm; not less than
6.35 μm but less than 8.00 μm; not less than 8.00 μm but less
than 10.08 μm; not less than 10.08 μm but less than 12.70 μm;
not less than 12.70 μm but less than 16.00 μm; not less than 16.00
μm but less than 20.20 μm; not less than 20.20 μm but less than
25.40 μm; not less than 25.40 μm but less than 32.00 μm; and not
less than 32.00 μm but less than 40.30 μm.

Measurement of Average Circularity

[0263] The shapes of toner particles are determined by passing a
suspension liquid containing toner particles through a detecting band in
an imaging area on a flat plate, optically detecting images of the toner
particles with a CCD camera, and analyzing the images. Specifically, the
average circularity is determined by dividing the peripheral length of a
circle having the same area as a projected image of a toner particle
detected as above by the peripheral length of the projected image.

[0264] The average circularity is measured by a flow-type particle image
analyzer FPIA-2000 (from Sysmex Corporation) as follows. Add 0.1 to 0.5
ml of a surfactant (e.g., an alkylbenzene sulfonate) to 100 to 150 ml of
water from which solid impurities have been removed, and further add 0.1
to 0.5 g of a sample thereto. Subject the resulting suspension to a
dispersion treatment with an ultrasonic disperser for about 1 to 3
minutes. Subject the suspension containing 3,000 to 10,000 particles per
micro-liter to a measurement of shape distribution of the sample with
above instrument.

Measurement of Volume Average Particle Diameter of Fine Resin Particles

[0265] The volume average particle diameter of fine resin particles is
measured by a Nanotrac Wave Particle Analyzer UPA-EX150 with Dynamic
Light Scattering Technology (from Nikkiso Co., Ltd.). Specifically, a
dispersion liquid containing fine resin particles having a predetermined
concentration is subjected to a measurement. A solvent of the dispersion
liquid alone is previously subjected to the measurement as a background.
Fine resin particles having a volume average particle diameter of several
tens nm to several μm are to be measured by the above procedure.

Measurement of Molecular Weight

[0266] Molecular weights of resins, such as polyester and vinyl resins,
are measured by GPC (gel permeation chromatography) under the following
conditions.

[0267] Instrument: HLC-8220GPC (from Tosoh Corporation)

[0268] Columns: TSKgel SuperHZM-M×3

[0269] Measuring temperature:
40° C.

[0270] Solvent: THF (Tetrahydrofuran)

[0271] Flow rate:
0.35 ml/min

[0272] Sample concentration: 0.05-0.6%

[0273] Injection
amount: 0.01 ml

[0274] The weight average molecular weight (Mw) is determined from a
molecular weight distribution curve thus obtained with reference to a
calibration curve complied with monodisperse polystyrene standard
samples. Each of the used monodisperse polystyrene standard samples has a
molecular weight of 5.8×100, 1.085×10,000, 5.95×10,000,
3.2×100,000, 2.56×1,000,000, 2.93×1,000,
2.85×10,000, 1.48×100,000, 8.417×100,000, and
7.5×1,000,000.

Measurement of Glass Transition Temperature and Endothermic Quantity

[0275] Glass transition temperature of a resin is measured by a
differential scanning calorimeter (e.g., DSC-6220R from Seiko Instruments
Inc.) as follows. Heat a sample from room temperature to 150° C.
at a heating rate of 10° C./min, allow it to stand for 10 minutes
at 150° C., cool it to room temperature, allow it to stand for 10
minutes at room temperature, and reheat it to 150° C. at a heating
rate of 10° C./min, thus obtaining an endothermic curve. Glass
transition temperature is determined from a middle point on the
endothermic curve between two baselines drawn at above and below that
point.

[0276] Endothermic quantity and melting point of release agents,
crystalline resins, and toners can also be determined from the
endothermic curve. Endothermic quantity is determined by calculating a
peak area of an endothermic peak. Generally, a release agent is meltable
at a lower temperature than a temperature at which a toner is to be
fixed. The heat of melting of the release agent is observed as an
endothermic peak in the endothermic curve. Some release agents generate
heat of transition due to the occurrence of phase transition in a solid
phase. In such cases, the total heat of melting and transition is used
for calculating endothermic quantity. Melting point is determined from a
temperature at which an endothermic peak has a local minimum value.

[0277] Toners are subjected to a measurement of melting point before being
mixed with an external additive.

[0278] The amount of a crystalline resin included in a toner is determined
as follows. Heat a toner in an amount of about 5 mg from -20° C.
to 150° C. at an average heating rate of 1° C./min and a
temperature amplitude of 0.5° C./60 sec by a differential scanning
calorimeter (e.g., temperature-modulated differential scanning
calorimeter Q200 from TA Instruments), thus measuring the amount of heat
of melting. The amount of heat of melting thus measured is converted into
the amount of a crystalline resin with reference to a calibration curve
or the heat of melting determined from a single body of the crystalline
resin.

Evaluation of Chargeability (Background Contamination)

[0279] Contain a toner in a cartridge for black toner in a printer IPSIO
SP C220 (from Ricoh Co., Ltd.). Print a 5% chart, i.e., a test chart No.
8 issued by The Imaging Society of Japan, on a sheet of white paper.
Visually observe the white paper and photoreceptor to determine whether
toner particles have soiled them or not.

[0280] A: No toner particle is observed on either the white paper or the
photoreceptor.

[0281] B: No toner particle is observed on the white paper but a slight
amount of toner particles are observed on the photoreceptor viewed at an
angle.

[0282] C: A slight amount of toner particles are observed on the white
paper viewed at an angle.

[0283] D: An amount of toner particles are clearly observed on the white
paper.

Evaluation of Resistance to Sticking

[0284] Observe the image printed above to determine whether undesired
white lines are generated or not. Observe the regulation blade, having
been in contact with the developing roller, to determine whether toner
particles are stuck thereto or not.

[0285] A: No white line is observed in the image. No toner particle is
observed to be stuck to the regulation blade.

[0286] B: No white line is observed in the image. A slight amount of toner
particles are observed to be stuck to the regulation blade but easily
releasable when being scratched slightly.

[0287] C: White lines are slightly observed in the image. A slight amount
of toner particles are observed to be stuck to the regulation blade and
not releasable even when being scratched slightly.

[0288] D: White lines are observed in the image. An amount of toner
particles are observed to be stuck to the regulation blade.

Evaluation of Low-Temperature Fixability

[0289] Contain a toner in a printer IPSIO SP C220 (from Ricoh Co., Ltd.)
which has been modified. Produce an unfixed solid image having a size of
50 mm×50 mm and toner particles in an amount of 10 g/m2 on 19
sheets of paper TYPE 6200Y (from Ricoh Co., Ltd.).

[0290] Pass each of the unfixed solid images through a modified fixing
unit at a system speed of 280 mm/sec to fix each solid image on each
sheet while varying the fixing temperature to 120° C. to
200° C. at an interval of 5° C. Fold each sheet with the
fixed solid image inside and reopen it. Slightly rub the fixed solid
image with an eraser. The minimum fixable temperature is defined as the
lowest temperature at which the fold line does not disappear.

[0291] A: The minimum fixable temperature is less than 100° C.

[0292] B: The minimum fixable temperature is not less than 100° C.
but less than 110° C.

[0293] C: The minimum fixable temperature is not less than 110° C.
but less than 120° C.

[0294] D: The minimum fixable temperature is not less than 120° C.

Evaluation of Heat-Resistant Storage Stability

[0295] Contain a toner in an amount of 25 g in a 50-ml glass vial, allow
it to stand for 24 hours in a constant-temperature chamber at 55°
C., and cool it to 24° C. Subject the toner to a penetration test
according to JIS K2235-1991 to measure penetration. The greater the
penetration, the better the heat-resistant storage stability. A toner
with the penetration less than 10 mm may cause a problem in practical
use. Penetration is graded into the following levels.

[0296] A: Penetration is not less than 20 mm.

[0297] B: Penetration is not less than 15 mm and less than 20 mm.

[0298] C: Penetration is not less than 10 mm and less than 15 mm.

[0299] D: Penetration is less than 10 mm.

Preparation of Crystalline Polyester Resin C-1

[0300] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 353 parts of 1,10-decanediol, 289 parts of
adipic acid, and 0.8 parts of dibutyltin oxide. Subject the mixture to a
reaction for 6 hours at 180° C. under normal pressure. Further
subject the mixture to a reaction for 4 hours under reduced pressure of
10 to 15 mmHg. Thus, a crystalline polyester resin C-1 is prepared. The
crystalline polyester resin C-1 has a number average molecular weight of
14,000, a weight average molecular weight of 33,000, and a melting point
of 65° C. The endothermic quantity gets maximum at the melting
point.

Preparation of Crystalline Polyester Resin C-2

[0301] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 160 parts of 1,9-nonanediol, 208 parts of
1,10-dodecanedioic acid, 5.92 parts of dimethyl 5-sulfoisophthalate
sodium salt, 16.7 parts of 5-t-butylisophthalic acid, and 0.4 parts of
dibutyltin oxide. Subject the mixture to a reaction for 6.5 hours at
180° C. under normal pressure. Further subject the mixture to a
reaction for 4 hours at 220° C. under reduced pressure of 10 to 15
mmHg. Thus, a crystalline polyester resin C-2 is prepared. The
crystalline polyester resin C-2 has a number average molecular weight of
4,200, a weight average molecular weight of 15,000, and a melting point
of 72° C. The endothermic quantity gets maximum at the melting
point.

Preparation of Crystalline Polyester Resin C-3

[0302] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 124 parts of ethylene glycol, 139 parts of
adipic acid, 2.96 parts of dimethyl 5-sulfoisophthalate sodium salt, 7.78
parts of 5-t-butylisophthalic acid, and 0.4 parts of dibutyltin oxide.
Subject the mixture to a reaction for 5 hours at 180° C. under
normal pressure. After removing the excessive ethylene glycol by
distillation under reduced pressure, subject the mixture to a reaction
for 2.5 hours at 220° C. under reduced pressure of 10 to 15 mmHg.
Thus, a crystalline polyester resin C-3 is prepared. The crystalline
polyester resin C-3 has a number average molecular weight of 3,400, a
weight average molecular weight of 10,000, and a melting point of
47° C. The endothermic quantity gets maximum at the melting point.

Preparation of Crystalline Polyester Resin C-4

[0303] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 353 parts of 1,10-decanediol, 289 parts of
adipic acid, and 0.8 parts of dibutyltin oxide. Subject the mixture to a
reaction for 8 hours at 180° C. under normal pressure. Further
subject the mixture to a reaction for 6 hours under reduced pressure of
10 to 15 mmHg. Thus, a crystalline polyester resin C-4 is prepared. The
crystalline polyester resin C-4 has a number average molecular weight of
18,000, a weight average molecular weight of 53,000, and a melting point
of 67° C. The endothermic quantity gets maximum at the melting
point.

Preparation of Crystalline Polyester Resin C-5

[0304] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 174 parts of 1,10-decanediol, 289 parts of
adipic acid, and 0.4 parts of dibutyltin oxide. Subject the mixture to a
reaction for 5 hours at 180° C. under normal pressure. Further
subject the mixture to a reaction for 2 hours under reduced pressure of
10 to 15 mmHg. Thus, a crystalline polyester resin C-5 is prepared. The
crystalline polyester resin C-5 has a number average molecular weight of
3,600, a weight average molecular weight of 12,000, and a melting point
of 60° C. The endothermic quantity gets maximum at the melting
point.

Preparation of Modified Polyester Resin D-1

[0305] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 241 parts of sebacic acid, 31 parts of adipic
acid, 164 parts of 1,4-butanediol, and 0.75 parts of
dihydroxybis(triethanolaminato) titanium as a condensation catalyst.
Subject the mixture to a reaction for 8 hours at 180° C. under
nitrogen gas flow while removing the produced water. Gradually heat the
mixture to 225° C. and subject it to a reaction for 4 hours under
nitrogen gas flow while removing the produced water and 1,4-butanediol.
Further subject the mixture to a reaction under reduced pressure of 5 to
20 mmHg until the weight average molecular weight reaches 18,000.

[0306] Charge another reaction vessel equipped with a condenser, a
stirrer, and a nitrogen inlet pipe with 218 parts of the above-prepared
crystalline resin, 250 parts of ethyl acetate, and 82 parts of
hexamethylene diisocyanate (HDI). Subject the mixture to a reaction for 5
hours at 80° C. under nitrogen gas flow. Remove the ethyl acetate
under reduced pressure. Thus, a modified polyester resin D-1 (i.e., a
polyester/polyurethane resin) is prepared. The modified polyester resin
has a weight average molecular weight of about 52,000 and a melting point
of 65° C. The endothermic quantity gets maximum at the melting
point.

Preparation of Crystalline Polyurea Resin E-1

[0307] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 79 parts (0.90 mol) of 1,4-butanediamine, 116
parts (1.00 mol) of 1,6-hexanediamine, and 600 parts of methyl ethyl
ketone (MEK), and agitate the mixture. Further add 475 parts (1.90 mol)
of 4,4'-diphenylmethane diisocyanate to the vessel and subject the
mixture to a reaction for 4 hours at 60° C. under nitrogen gas
flow. Remove the MEK under reduced pressure. Thus, a crystalline polyurea
resin E-1 is prepared. The crystalline polyurea resin E-1 has a weight
average molecular weight of 46,000 and a melting point of 62° C.
The endothermic quantity gets maximum at the melting point.

Preparation of Urethane-Modified Crystalline Polyester Resin F-1

[0308] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 202 parts (1.00 mol) of sebacic acid, 189
parts (1.60 mol) of 1,6-hexanediol, and 0.5 parts of dibutyltin oxide as
a condensation catalyst. Subject the mixture to a reaction for 8 hours at
180° C. under nitrogen gas flow while removing the produced water.
Gradually heat the mixture to 220° C. and subject it to a reaction
for 4 hours under nitrogen gas flow while removing the produced water and
1,6-hexanediol. Further subject the mixture to a reaction under reduced
pressure of 5 to 20 mmHg until the weight average molecular weight
reaches 7,000. Thus, a crystalline polyester resin F'-1 is prepared. The
crystalline polyester resin F'-1 has a weight average molecular weight of
7,000.

[0309] Charge another reaction vessel equipped with a condenser, a
stirrer, and a nitrogen inlet pipe with the above-prepared crystalline
polyester resin F'-1, 300 parts of ethyl acetate, and 38 parts (0.15 mol)
of 4,4'-diphenylmethane diisocyanate (MDI). Subject the mixture to a
reaction for 5 hours at 80° C. under nitrogen gas flow. Remove the
ethyl acetate under reduced pressure. Thus, a urethane-modified
crystalline polyester resin F-1 is prepared. The urethane-modified
crystalline polyester resin F-1 has a weight average molecular weight of
15,000 and a melting point of 65° C. The endothermic quantity gets
maximum at the melting point.

Preparation of Crystalline Resin Precursor G-1

[0310] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 202 parts (1.00 mol) of sebacic acid, 122
parts (1.03 mol) of 1,6-hexanediol, and 0.5 parts of
dihydroxybis(triethanolaminato) titanium as a condensation catalyst.
Subject the mixture to a reaction for 8 hours at 180° C. under
nitrogen gas flow while removing the produced water. Gradually heat the
mixture to 220° C. and subject it to a reaction for 4 hours under
nitrogen gas flow while removing the produced water and 1,6-hexanediol.
Further subject the mixture to a reaction under reduced pressure of 5 to
20 mmHg until the weight average molecular weight reaches 25,000.

[0311] Charge another reaction vessel equipped with a condenser, a
stirrer, and a nitrogen inlet pipe with the above-prepared crystalline
resin, 300 parts of ethyl acetate, and 27 parts (0.16 mol) of
hexamethylene diisocyanate (HDI). Subject the mixture to a reaction for 5
hours at 80° C. under nitrogen gas flow. Thus, a 50% ethyl acetate
solution of a crystalline resin precursor G-1 having an isocyanate group
on its terminal is prepared.

[0312] Mix 10 parts of the ethyl acetate solution of the crystalline resin
precursor G-1 with 10 parts of tetrahydrofuran (THF) and 1 part of
dibutylamine. Agitate the mixture for 2 hours. As a result of a GPC
measurement of the ethyl acetate solution, the crystalline resin
precursor G-1 has a weight average molecular weight of 53,000. As a
result of a DSC measurement, the crystalline resin precursor G-1 has a
melting point of 57° C. The endothermic quantity gets maximum at
the melting point.

Preparation of Amorphous Polyester Resin A-1

[0313] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 229 parts of ethylene oxide 2 mol adduct of
bisphenol A, 529 parts of propylene oxide 3 mol adduct of bisphenol A,
208 parts of terephthalic acid, 46 parts of adipic acid, and 2 parts of
dibutyltin oxide. Subject the mixture to a reaction for 8 hours at
230° C. under normal pressure. Further subject the mixture to a
reaction for 5 hours under reduced pressure of 10 to 15 mmHg. After
adding 44 parts of trimellitic anhydride to the vessel, further subject
the mixture to a reaction for 2 hours at 180° C. under normal
pressure. Thus, an amorphous polyester resin A-1 is prepared. The
amorphous polyester resin A-1 has a number average molecular weight of
2,500, a weight average molecular weight of 6,700, a glass transition
temperature of 43° C., and an acid value of 25 mgKOH/g.

[0315] Charge a beaker with 20 parts of a copper phthalocyanine, 4 parts
of a colorant dispersant (SOLSPERSE 28000 from Avecia), and 76 parts of
ethyl acetate. Subject the mixture to a dispersion treatment with a bead
mill to finely disperse the copper phthalocyanine. Thus, a colorant
dispersion liquid 1 is prepared. The colorant particles dispersed in the
colorant dispersion liquid 1 has a volume average particle diameter of
0.3 μm measured by particle analyzer LA-920 from Horiba, Ltd.

Preparation of Release Agent Dispersant 1

[0316] Charge an autoclave reaction vessel equipped with a thermometer and
a stirrer with 454 parts of xylene and 150 parts of a
low-molecular-weight polyethylene (SANWAX LEL-400 from Sanyo Chemical
Industries, Ltd., having a softening point of 128° C.). After
replacing the air in the vessel with nitrogen gas, heat the mixture to
170° C. to be melted. Drop a mixture liquid of 595 parts of
styrene, 255 parts of methyl methacrylate, 34 parts of
di-t-butylperoxyhexahydroterephthalate, and 119 parts of xylene in the
vessel over a period of 3 hours at 170° C. Subject the mixture to
a polymerization and keep it at that temperature for 30 minutes. Remove
the solvent thereafter. Thus, a release agent dispersant 1 is prepared.
The release agent dispersant 1 has a number average molecular weight of
1,872, a weight average molecular weight of 5,194, and a glass transition
temperature of 56.9° C.

Preparation of Wax Dispersion Liquid

[0317] Charge a reaction vessel equipped with a thermometer and a stirrer
with 10 parts of a paraffin wax (having a melting point of 73°
C.), 1 part of the release agent dispersant 1, and 33 parts of ethyl
acetate. Heat the mixture to 78° C. so that the wax is dissolved
in the ethyl acetate. Cool the resulting solution to 30° C. over a
period of 1 hour so that the wax is crystallized into the form of fine
particles. Subject the solution to a wet pulverization treatment with a
ULTRA VISCO MILL (from Aimex Co., Ltd.). Thus, a wax dispersion liquid 1
is prepared.

Preparation of Fine Vinyl Resin Particle Dispersion Liquid V-1

[0318] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 0.7 parts of sodium dodecyl sulfate and 498
parts of ion-exchange water. Heat the mixture to 80° C. while
agitating it so that the sodium dodecyl sulfate is dissolved in the
ion-exchange water. Add a solution in which 2.6 parts of potassium
persulfate are dissolved in 104 parts of ion-exchange water to the
vessel. After 15 minutes, drop a monomer mixture liquid including 200
parts of styrene monomer and 4.2 parts of n-octanethiol in the vessel
over a period of 90 minutes. Keep the mixture at 80° C. for
subsequent 60 minutes and subject it to a polymerization reaction.

[0319] Cool the mixture thereafter. Thus, a fine vinyl resin particle
dispersion liquid V-1 containing white fine vinyl resin particles having
a volume average particle diameter of 130 nm is prepared. The solid
content is about 25%. Put 2 ml of the fine vinyl resin particle
dispersion liquid V-1 on a petri dish and vaporize the dispersion
solvent. The dried residue has a number average molecular weight of
9,500, a weight average molecular weight of 18,000, and a glass
transition temperature of 83° C.

Preparation of Fine Vinyl Resin Particle Dispersion Liquid V-2

[0320] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 0.7 parts of sodium dodecyl sulfate and 498
parts of ion-exchange water. Heat the mixture to 80° C. while
agitating it so that the sodium dodecyl sulfate is dissolved in the
ion-exchange water. Add a solution in which 2.5 parts of potassium
persulfate are dissolved in 98 parts of ion-exchange water to the vessel.
After 15 minutes, drop a monomer mixture liquid including 160 parts of
styrene monomer and 40 parts of methoxypolyethylene glycol methacrylate
(ED=2 mol) (M-20G from Shin-Nakamura Chemical Co., Ltd.) in the vessel
over a period of 90 minutes. Keep the mixture at 80° C. for
subsequent 60 minutes and subject it to a polymerization reaction.

[0321] Cool the mixture thereafter. Thus, a fine vinyl resin particle
dispersion liquid V-2 containing white fine vinyl resin particles having
a volume average particle diameter of 115 nm is prepared. The solid
content is about 25%. Put 2 ml of the fine vinyl resin particle
dispersion liquid V-2 on a petri dish and vaporize the dispersion
solvent. The dried residue has a number average molecular weight of
98,000, a weight average molecular weight of 420,000, and a glass
transition temperature of 70° C.

Preparation of Fine Vinyl Resin Particle Dispersion Liquid V-3

[0322] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 0.7 parts of sodium dodecyl sulfate and 498
parts of ion-exchange water. Heat the mixture to 80° C. while
agitating it so that the sodium dodecyl sulfate is dissolved in the
ion-exchange water. Add a solution in which 2.7 parts of potassium
persulfate are dissolved in 108 parts of ion-exchange water to the
vessel. After 15 minutes, drop a monomer mixture liquid including 160
parts of styrene monomer and 40 parts of methyl methacrylate in the
vessel over a period of 90 minutes. Keep the mixture at 80° C. for
subsequent 60 minutes and subject it to a polymerization reaction.

[0323] Cool the mixture thereafter. Thus, a fine vinyl resin particle
dispersion liquid V-3 containing white fine vinyl resin particles having
a volume average particle diameter of 100 nm is prepared. The solid
content is about 25%. Put 2 ml of the fine vinyl resin particle
dispersion liquid V-3 on a petri dish and vaporize the dispersion
solvent. The dried residue has a number average molecular weight of
60,000, a weight average molecular weight of 216,000, and a glass
transition temperature of 99° C.

Preparation of Fine Vinyl Resin Particle Dispersion Liquid V-4

[0324] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 0.7 parts of sodium dodecyl sulfate and 498
parts of ion-exchange water. Heat the mixture to 80° C. while
agitating it so that the sodium dodecyl sulfate is dissolved in the
ion-exchange water. Add a solution in which 2.6 parts of potassium
persulfate are dissolved in 102 parts of ion-exchange water to the
vessel. After 15 minutes, drop a monomer mixture liquid including 184.6
parts of styrene monomer, 15 parts of butyl acrylate, and 0.5 parts of
divinylbenzene in the vessel over a period of 90 minutes. Keep the
mixture at 80° C. for subsequent 60 minutes and subject it to a
polymerization reaction.

[0325] Cool the mixture thereafter. Thus, a fine vinyl resin particle
dispersion liquid V-4 containing white fine vinyl resin particles having
a volume average particle diameter of 79 nm is prepared. The solid
content is about 25%. Put 2 ml of the fine vinyl resin particle
dispersion liquid V-4 on a petri dish and vaporize the dispersion
solvent. The dried residue has a number average molecular weight of
34,000, a weight average molecular weight of 160,000, and a glass
transition temperature of 87° C.

Preparation of Fine Vinyl Resin Particle Dispersion Liquid V-5

[0326] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 0.7 parts of sodium dodecyl sulfate and 498
parts of ion-exchange water. Heat the mixture to 80° C. while
agitating it so that the sodium dodecyl sulfate is dissolved in the
ion-exchange water. Add a solution in which 2.6 parts of potassium
persulfate are dissolved in 104 parts of ion-exchange water to the
vessel. After 15 minutes, drop a monomer mixture liquid including 200
parts of styrene monomer in the vessel over a period of 90 minutes. Keep
the mixture at 80° C. for subsequent 60 minutes and subject it to
a polymerization reaction.

[0327] Cool the mixture thereafter. Thus, a fine vinyl resin particle
dispersion liquid V-5 containing white fine vinyl resin particles having
a volume average particle diameter of 100 nm is prepared. The solid
content is about 25%. Put 2 ml of the fine vinyl resin particle
dispersion liquid V-5 on a petri dish and vaporize the dispersion
solvent. The dried residue has a number average molecular weight of
62,000, a weight average molecular weight of 215,000, and a glass
transition temperature of 101° C.

Preparation of Fine Vinyl Resin Particle Dispersion Liquid V-6

[0328] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 0.7 parts of sodium dodecyl sulfate and 498
parts of ion-exchange water. Heat the mixture to 80° C. while
agitating it so that the sodium dodecyl sulfate is dissolved in the
ion-exchange water. Add a solution in which 2.6 parts of potassium
persulfate are dissolved in 104 parts of ion-exchange water to the
vessel. After 15 minutes, drop a monomer mixture liquid including 200
parts of styrene monomer and 14 parts of n-octanethiol in the vessel over
a period of 90 minutes. Keep the mixture at 80° C. for subsequent
60 minutes and subject it to a polymerization reaction.

[0329] Cool the mixture thereafter. Thus, a fine vinyl resin particle
dispersion liquid V-6 containing white fine vinyl resin particles having
a volume average particle diameter of 103 nm is prepared. The solid
content is about 25%. Put 2 ml of the fine vinyl resin particle
dispersion liquid V-6 on a petri dish and vaporize the dispersion
solvent. The dried residue has a number average molecular weight of
2,700, a weight average molecular weight of 6,700, and a glass transition
temperature of 44° C.

Preparation of Fine Vinyl Resin Particle Dispersion Liquid V-7

[0330] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 0.7 parts of sodium dodecyl sulfate and 498
parts of ion-exchange water. Heat the mixture to 80° C. while
agitating it so that the sodium dodecyl sulfate is dissolved in the
ion-exchange water. Add a solution in which 2.7 parts of potassium
persulfate are dissolved in 108 parts of ion-exchange water to the
vessel. After 15 minutes, drop a monomer mixture liquid including 100
parts of styrene monomer and 90 parts of methyl methacrylate in the
vessel over a period of 90 minutes. Keep the mixture at 80° C. for
subsequent 60 minutes and subject it to a polymerization reaction.

[0331] Cool the mixture thereafter. Thus, a fine vinyl resin particle
dispersion liquid V-7 containing white fine vinyl resin particles having
a volume average particle diameter of 102 nm is prepared. The solid
content is about 25%. Put 2 ml of the fine vinyl resin particle
dispersion liquid V-7 on a petri dish and vaporize the dispersion
solvent. The dried residue has a number average molecular weight of
57,000, a weight average molecular weight of 186,000, and a glass
transition temperature of 100° C.

Preparation of Fine Vinyl Resin Particle Dispersion Liquid V-8

[0332] Mix 100 parts of the fine vinyl resin particle dispersion liquid
V-1 with 100 parts of the fine vinyl resin particle dispersion liquid
V-4. Thus, a fine vinyl resin particle dispersion liquid V-8 is prepared.
The solid content is about 25%. Put 2 ml of the fine vinyl resin particle
dispersion liquid V-8 on a petri dish and vaporize the dispersion
solvent. The dried residue has a number average molecular weight of
27,000, a weight average molecular weight of 90,000, and a glass
transition temperature of 85° C.

Preparation of Fine Vinyl Resin Particle Dispersion Liquid V-9

[0333] Charge a reaction vessel equipped with a condenser, a stirrer, and
a nitrogen inlet pipe with 0.7 parts of sodium dodecyl sulfate and 498
parts of ion-exchange water. Heat the mixture to 80° C. while
agitating it so that the sodium dodecyl sulfate is dissolved in the
ion-exchange water. Add a solution in which 2.5 parts of potassium
persulfate are dissolved in 98 parts of ion-exchange water to the vessel.
After 15 minutes, drop a monomer mixture liquid including 130 parts of
styrene monomer and 70 parts of methoxypolyethylene glycol methacrylate
in the vessel over a period of 90 minutes. Keep the mixture at 80°
C. for subsequent 60 minutes and subject it to a polymerization reaction.

[0334] Cool the mixture thereafter. Thus, a fine vinyl resin particle
dispersion liquid V-9 containing white fine vinyl resin particles having
a volume average particle diameter of 115 nm is prepared. The solid
content is about 25%. Put 2 ml of the fine vinyl resin particle
dispersion liquid V-9 on a petri dish and vaporize the dispersion
solvent. The dried residue has a number average molecular weight of
87,600, a weight average molecular weight of 392,000, and a glass
transition temperature of 48° C.

[0335] Properties of the above-prepared vinyl resins are shown in Table 2.

[0336] Charge a reaction vessel equipped with a thermometer and a stirrer
with 100 parts of the crystalline polyester resin C-1 and 100 parts of
ethyl acetate. Heat the mixture to 50° C. and uniformly agitate
it. Thus, a resin solution 1 is prepared.

[0337] Charge a beaker with 60 parts of the resin solution 1, 27 parts of
the wax dispersion liquid, and 10 parts of the colorant dispersion liquid
1. Uniformly agitate the mixture with a TK HOMOMIXER at a revolution of
8,000 rpm at 50° C. Thus, a toner constituent liquid 1 is
prepared.

[0339] Add 75 parts of the toner constituent liquid to the beaker at
50° C. while agitating the mixture with a TK HOMOMIXER at a
revolution of 10,000 rpm. Further agitate the mixture for 2 minutes.
Thus, a slurry 1 is prepared.

[0340] While agitating the slurry 1 with a THREE-ONE MOTOR at a revolution
of 200 rpm at 25° C., drop 21.4 parts of the fine vinyl resin
particle dispersion liquid V-1 in the slurry 1 over a period of 5
minutes. Keep agitating the mixture for 30 minutes. Take out a small
amount of the slurry, dilute it with 10 times as much water, and subject
it to centrifugal separation. As a result, core particles settle down at
the bottom of a test tube while the supernatant liquid being
substantially transparent. Thus, a projection-formed slurry 1 is
prepared.

Solvent Removal

[0341] Subject the projection-formed slurry 1 to solvent removal for 8
hours at 30° C. in a vessel equipped with a stirrer and a
thermometer. Thus, a dispersion slurry 1 is prepared.

[0343] (1) Mix the filtration residue with 100 parts of ion-exchange water
with a TK HOMOMIXER for 10 minutes at a revolution of 12,000 rpm and
subject the mixture to a filtration.

[0344] (2) Mix the filtration residue with 100 parts of ion-exchange water
with a TK HOMOMIXER for 30 minutes at a revolution of 12,000 rpm while
applying ultrasonic vibration. Subject the mixture to a filtration under
reduced pressure. Repeat this operation until the re-slurry liquid
exhibits an electric conductivity of 10 μS/cm or less.

[0345] (3) Add a 10% solution of hydrochloric acid to the re-slurry liquid
until the re-slurry liquid exhibits a pH of 4. Agitate the re-slurry
liquid for 30 minutes with a THREE-ONE MOTOR and subject it to a
filtration.

[0346] (4) Mix the filtration residue with 100 parts of ion-exchange water
with a TK HOMOMIXER for 10 minutes at a revolution of 12,000 rpm and
subject the mixture to a filtration. Repeat this operation until the
re-slurry liquid exhibits an electric conductivity of 10 μS/cm or
less. Thus, a filtered cake 1 is obtained.

[0347] Subject the remaining dispersion slurry 1 to the same procedure and
add the resulting filtered cake to the above filtered cake 1.

[0348] Dry the filtered cake 1 by a circulating drier for 48 hours at
45° C. and sieve it with a mesh having openings of 75 μm. Thus,
a mother toner 1 is prepared. Mix 50 parts of the mother toner 1 with 1
part of a hydrophobized silica having a primary particle diameter of
about 30 nm and 0.5 parts of a hydrophobized silica having a primary
particle diameter of about 10 nm with a HENSCHEL MIXER. Thus, a toner 1
is prepared. Subject the toner 1 to an observation with a scanning
electron microscopy (SEM) to determine the lengths of the long sides of
the projections and the surface coverage of the toner with the
projections. The average length of the long sides of the projections is
0.24 μm, the standard deviation of the lengths of the long sides of
the projections is 0.132, and the surface coverage of the toner with the
projections is 57%.

Example 2

[0349] Charge a reaction vessel equipped with a thermometer and a stirrer
with 95 parts of the crystalline polyester resin C-1, 5 parts of the
amorphous polyester resin A-1, and 100 parts of ethyl acetate. Heat the
mixture to 50° C. and uniformly agitate it. Thus, a resin solution
2 is prepared. Repeat the procedure for preparing the toner 1 except for
replacing the resin solution 1 with the resin solution 2. Thus, a toner 2
is prepared.

[0361] Charge a reaction vessel equipped with a thermometer and a stirrer
with 75 parts of the crystalline polyester resin C-1, 25 parts of the
amorphous polyester resin A-1, and 100 parts of ethyl acetate. Heat the
mixture to 50° C. and uniformly agitate it. Thus, a resin solution
14 is prepared. Repeat the procedure for preparing the toner 1 except for
replacing the resin solution 1 with the resin solution 14. Thus, a toner
14 is prepared.

Example 15

[0362] Repeat the procedure for preparing the toner 1 except for replacing
the crystalline polyester resin C-1 with 90 parts of the crystalline
polyester resin C-1 and 10 parts of the modified polyester resin D-1.
Thus, a toner 15 is prepared.

Example 16

[0363] Repeat the procedure for preparing the toner 1 except for replacing
the crystalline polyester resin C-1 with the crystalline polyurea resin
E-1. Thus, a toner 16 is prepared.

Example 17

[0364] Repeat the procedure for preparing the toner 1 except for replacing
the crystalline polyester resin C-1 with 70 parts of the
urethane-modified crystalline polyester resin F-2 and 30 parts of the
crystalline resin precursor G-1. Thus, a toner 17 is prepared.

Comparative Example 1

[0365] Repeat the procedure for preparing the toner 1 except for replacing
the crystalline polyester resin C-1 with the amorphous polyester resin
A-1. Thus, a toner 16 is prepared.

Comparative Example 2

[0366] Repeat the procedure for preparing the toner 1 except that the
process of forming projection is not performed. Thus, a toner 17 is
prepared. As a result of a SEM observation of the toner 17, the surface
is observed to be substantially smooth and to have no projection having a
long side of 0.15 μm or more.

Comparative Example 3

[0367] Repeat the procedure for preparing the toner 1 except that the fine
vinyl resin particle dispersion liquid V-1 is previously added to the
aqueous phase and the process of forming projection is not performed.
Thus, a toner 18 is prepared.

[0370] Repeat the procedure for preparing the toner 1 except for changing
the amount of the fine vinyl resin particle dispersion liquid V-1 from
21.4 parts to 107 parts and 21 parts of the 48.5% aqueous solution of
dodecyl diphenyl ether sodium disulfonate is added at the same time as
the fine vinyl resin particle dispersion liquid V-1 is added. Thus, a
toner 21 is prepared.

[0371] Properties of the above-prepared toners are shown in Tables 3-1 and
3-2. In Tables 3-1 and 3-2, "Binder Resin 1" represents a crystalline
polyester resin.

[0373] Additional modifications and variations in accordance with further
embodiments of the present invention are possible in light of the above
teachings. It is therefore to be understood that within the scope of the
appended claims the invention may be practiced other than as specifically
described herein.

Patent applications by Atsushi Yamamoto, Shizuoka JP

Patent applications by Daiki Yamashita, Kanagawa JP

Patent applications by Hideyuki Santo, Shizuoka JP

Patent applications by Masahide Yamada, Shizuoka JP

Patent applications by Shinya Nakayama, Shizuoka JP

Patent applications by Suzuka Amemori, Shizuoka JP

Patent applications in class Developing composition or product

Patent applications in all subclasses Developing composition or product